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RADIOLOGY - COMPLETE ANSWERS

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Q1. Hematuria: Role of Radiology (20 Marks)

Definition

Classification

1. Gross (macroscopic) hematuria - visible discoloration of urine
2. Microscopic hematuria - >3 RBC/HPF on properly collected midstream sample
3. Pseudohematuria - red urine without RBCs (beets, rifampicin, porphyria)

Causes of Hematuria

Radiological Modalities and Their Role

1. Plain X-Ray (KUB - Kidneys, Ureters, Bladder)

• First-line screening investigation
• Role: Detects radio-opaque calculi (80% of renal stones are radio-opaque; calcium oxalate, calcium phosphate, struvite)
• Identifies renal size, shape, and position
• Limitation: Cannot detect urothelial tumors, soft tissue lesions, radiolucent calculi (uric acid stones)

2. Ultrasonography (USG)

• Most widely used, non-ionizing, cost-effective first-line imaging
• Findings and role:
  • Renal masses: hypoechoic/echogenic lesions (RCC appears as solid heterogeneous mass with disruption of renal sinus fat; AML is highly echogenic)
  • Hydronephrosis: dilated pelvicalyceal system suggesting obstructing calculus/tumor
  • Renal calculi: hyperechoic foci with posterior acoustic shadowing
  • Bladder: intraluminal masses (echogenic, non-shadowing; sessile masses more suspicious), bladder wall thickness
  • Ureterocele: thin-walled cystic structure near ureteric orifice
  • Post-void residual urine volume
• Color Doppler: Demonstrates vascularity in renal tumors; differentiates vascular AVM from simple cysts; evaluates renal vein thrombosis in RCC
• Limitation: Limited sensitivity for ureteral evaluation, misses flat urothelial lesions, operator-dependent

3. Intravenous Urography (IVU / IVP)

• Historically the gold standard for upper urinary tract evaluation
• Technique: Sequential plain film + films at 5, 10, 15 minutes after IV contrast
• Role:
  • Detects filling defects in pelvicalyceal system, ureter (suggests TCC)
  • Demonstrates hydronephrosis, hydroureter
  • Shows function of each kidney (nephrogram)
  • Characterizes calyceal distortion by renal masses
  • Detects bladder filling defects
• Now largely replaced by CT urography but still used where CT is unavailable

4. CT Urography (CTU) - GOLD STANDARD

• The investigation of choice for hematuria workup
• Three-phase protocol:
  • Non-contrast phase: Detects calculi (hyperdense), pre-existing hemorrhage, calcifications in masses
  • Nephrographic (corticomedullary) phase (70-100 sec): Best for renal parenchymal masses - RCC, AML, oncocytoma; shows renal vein/IVC involvement
  • Excretory (urographic) phase (7-10 min): Contrast fills collecting system - demonstrates filling defects from TCC, blood clots, calculi
• Advantages over IVU:
  • Detects all types of calculi including radiolucent
  • Better characterization of renal masses (density, enhancement, morphology)
  • Staging of urological malignancies
  • Detects lymphadenopathy, metastases, extraurinary pathology
  • Sensitivity for upper tract TCC: 94% (vs 14% for USG)

5. MR Urography (MRU)

• Preferred in: Pregnancy, children, renal insufficiency, contrast allergy
• Uses heavily T2-weighted sequences (RARE/HASTE) to show fluid-filled structures without contrast
• Gadolinium-enhanced excretory phase similar to CTU
• Better soft tissue characterization than CT
• Limitation: Cannot detect calculi (low signal on MRI), longer acquisition time, expensive

6. Retrograde Pyelography

• Invasive procedure performed at cystoscopy
• Role: When CTU/IVU non-diagnostic; delineates ureteric filling defects and strictures
• High sensitivity for upper tract TCC
• Allows biopsy/brushing of suspicious lesions

7. Angiography / Digital Subtraction Angiography (DSA)

• Reserved for vascular causes of hematuria: AVM, arteriovenous fistula, renal artery aneurysm
• Therapeutic: embolization for bleeding renal masses, AVMs, trauma
• Renal artery aneurysm: saccular outpouching on angiography

8. Cystoscopy (not imaging but complementary)

• Direct visualization of bladder mucosa
• Essential for detecting flat urothelial carcinoma (CIS) and small papillary tumors missed on all imaging modalities

Algorithmic Approach to Radiological Evaluation

• CTU (gold standard) + Cystoscopy + Urine cytology

• USG kidneys and bladder (first line)
• If negative: follow-up urinalysis at 6 months

• Children/Pregnancy: USG first (avoid radiation)
• Renal insufficiency / contrast allergy: MR urography
• Suspected vascular cause: Color Doppler USG, then DSA

AUA Risk Stratification (2020, updated 2025)

• Low risk: Age <40, non-smoker, <25 RBC/HPF - USG + follow-up
• Intermediate risk: Age 40-59, smoking history, 25-100 RBC/HPF - USG + cystoscopy
• High risk: Age >60, heavy smoker, >100 RBC/HPF or any gross hematuria - CTU + cystoscopy

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Q2. Draw Cut Section of Kidney - Classify Congenital Anomalies of Urinary System - Three Renal Anomalies in Detail

Cut Section of Kidney

         CORTEX (outer zone, 1-1.5 cm thick)
        /  - Renal corpuscles (glomeruli + Bowman's capsule)
       /   - Proximal & distal convoluted tubules
      |    - Columns of Bertin (cortical tissue between pyramids)
      |
      |    MEDULLA (inner zone)
      |    - 8-18 Renal pyramids (striated appearance due to collecting ducts)
      |    - Apex = Renal papilla (opens into Minor calyx)
      |
      |    RENAL SINUS (central cavity, fat-filled)
      |    - Major calyces (2-3) → Renal Pelvis → Ureter
      |    - Minor calyces (8-12) receive papillae
      |    - Renal vessels and lymphatics
      |
       \   CAPSULE (thin fibrous layer)
        \
         Cortex → Medulla → Papilla → Minor calyx → Major calyx → Pelvis → Ureter

1. Fibrous capsule
2. Renal cortex (outer + columns of Bertin)
3. Medullary pyramids
4. Renal papilla
5. Minor calyx
6. Major calyx
7. Renal pelvis
8. Ureter (UPJ)
9. Renal sinus (fat)
10. Renal artery, vein, lymphatics

Classification of Congenital Anomalies of Urinary System

• Renal agenesis (unilateral / bilateral)
• Supernumerary kidney

• Renal ectopia (pelvic kidney, thoracic kidney, crossed ectopia)
• Malrotation

• Horseshoe kidney (most common fusion anomaly)
• Crossed fused ectopia
• Cake/Lump kidney

• Renal hypoplasia
• Multicystic dysplastic kidney (MCDK)
• Polycystic kidney disease (ARPKD, ADPKD)
• Medullary sponge kidney
• Simple cysts

• Non-rotation, malrotation

• Pelviureteric junction (PUJ) obstruction
• Ureteric duplication (bifid ureter, duplex system)
• Ureterocele
• Vesicoureteral reflux (VUR)
• Megaureter

• Bladder exstrophy
• Posterior urethral valves
• Hypospadias, epispadias

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Three Renal Anomalies in Detail

1. Horseshoe Kidney

• USG: Echogenic tissue crossing midline anterior to aorta; lower pole calyces oriented medially; axis of kidneys reversed (lower poles closer together)
• IVU: Lower pole calyces pointing medially; "inverted" renal axis; isthmus visible as density anterior to L3-L5 vertebrae; associated PUJ obstruction seen as dilated pelvis
• CT: Best modality - shows isthmus clearly (parenchymal or fibrous), level of fusion, vascular anatomy (multiple anomalous vessels), associated anomalies (PUJ obstruction, malrotation)
• DTPA/MAG3 scan: Evaluates differential function and drainage when PUJ obstruction suspected

• PUJ obstruction (30%) - due to high insertion of ureter, crossing vessels
• Vesicoureteral reflux
• Renal calculi (due to urinary stasis)
• Increased risk of Wilms tumor, TCC, carcinoid
• Associated with Turner syndrome, trisomy 18

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2. Multicystic Dysplastic Kidney (MCDK)

• Prenatal USG: Multiple cysts of varying sizes (the largest cyst is NOT central - distinguishes from hydronephrosis); NO identifiable renal sinus/pelvis; no communication between cysts
• Postnatal USG: Cluster of non-communicating cysts of varying sizes replacing the kidney; no normal renal tissue; hyperechoic stroma between cysts; contralateral kidney often shows compensatory hypertrophy; color Doppler shows absent or markedly diminished blood flow (no normal hilar vessels)
• DMSA scan: The most important investigation - shows absent/minimal function on the affected side (photopenic area). Confirms non-function; also evaluates contralateral kidney
• Voiding Cystourethrogram (VCUG): Done to exclude VUR (occurs in 18-43% contralateral kidney)
• CT/MRI: Used when USG inconclusive; confirms diagnosis, evaluates for complications

• MCDK: non-communicating cysts, no renal pelvis, variable cyst sizes, largest cyst peripheral
• Hydronephrosis: communicating dilated calyces with central pelvis, normal renal parenchyma around cysts

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3. Polycystic Kidney Disease - Autosomal Recessive (ARPKD)

• Bilateral enlarged, hyperechoic kidneys (innumerable tiny cysts below USG resolution - interfaces between cysts cause diffuse hyperechogenicity)
• Loss of corticomedullary differentiation
• Oligohydramnios (due to reduced fetal urine output)
• Absent or small bladder
• The cysts are too small to be individually resolved on USG

• Massively enlarged bilateral kidneys with diffuse hyperechogenicity
• Multiple tiny cysts may become visible (1-2 mm)
• Hepatomegaly, periportal fibrosis, dilated bile ducts (Caroli disease association)

• Bilaterally enlarged kidneys with a striated nephrogram on contrast
• "Sunburst" or radial pattern of enhancing collecting ducts extending from medulla to cortex
• Eventual macroscopic cyst formation with age

• T2: diffuse hyperintensity; individual tiny cysts visible
• Best for following disease progression

• Hypertension, CKD, ESRD
• Portal hypertension from hepatic fibrosis
• Esophageal varices
• Pulmonary hypoplasia (due to oligohydramnios)

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Q3. USG and CT Findings in Five Adrenal Lesions

1. Adrenal Adenoma (Most Common Adrenal Mass)

• Small (<3 cm), homogeneous, well-defined hypoechoic mass
• Round or oval
• No calcification usually
• Color Doppler: minimal vascularity

• Hallmark: LOW attenuation on non-contrast CT (< 10 HU) due to high lipid content
• Smooth, homogeneous, small
• Rapid washout on contrast: >50% absolute washout or >40% relative washout at 15 minutes (adenoma washes out contrast rapidly)
• Chemical shift MRI (not CT): signal drop on out-of-phase sequences

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2. Adrenal Pheochromocytoma

• Well-defined, round, heterogeneous mass
• Variable echogenicity (mixed solid-cystic due to hemorrhage/necrosis)
• Larger than adenoma typically (>3 cm)
• Color Doppler: hypervascular

• Large, heterogeneous adrenal mass with areas of necrosis, hemorrhage, and cystic change
• High attenuation on non-contrast CT (>10 HU, often >20 HU)
• INTENSE enhancement with contrast (>100 HU in arterial phase)
• Slow washout (unlike adenoma)
• Calcification in 10%
• Bilateral in 10%, malignant in 10%, extra-adrenal in 10%, familial in 10% ("rule of 10s")
• Caution: IV contrast administration requires alpha-blockade beforehand to avoid hypertensive crisis

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3. Adrenal Cortical Carcinoma (ACC)

• Large (often >6 cm at diagnosis), heterogeneous mass
• Mixed echogenicity with areas of necrosis
• Invasion of adjacent structures (IVC, kidney)
• Color Doppler: IVC tumor thrombus can be identified

• Large (>4-6 cm), irregular, heterogeneous mass
• Areas of central necrosis, hemorrhage, calcification (30%)
• Intense but heterogeneous enhancement
• High non-contrast attenuation (>20 HU)
• Local invasion: kidney, IVC, liver
• Lymphadenopathy, liver metastases, lung metastases
• IVC tumor thrombus (CT venography/MRI to characterize)
• No rapid contrast washout

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4. Adrenal Metastasis

• Usually bilateral (distinguishes from most primary lesions)
• Hypoechoic to heterogeneous
• Irregular margins if large
• Color Doppler: may show vascularity

• Variable size, often bilateral
• Non-contrast attenuation >10 HU (lipid-poor, unlike adenoma)
• Irregular, poorly defined margins
• Heterogeneous enhancement, slow washout
• Central necrosis in larger lesions
• Key: in known malignancy, any adrenal mass >1 cm is suspicious
• PET-CT: FDG avid (hot) - differentiates from benign adenoma (cold)

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5. Adrenal Myelolipoma

• Highly echogenic mass (due to fat content - similar to AML of kidney)
• Posterior acoustic enhancement
• Well-defined, homogeneous when small
• Heterogeneous with areas of myeloid tissue when large

• Diagnostic: Contains macroscopic fat (Hounsfield units <-30 HU in fat areas)
• Mixed attenuation mass: fat density (-30 to -100 HU) + soft tissue myeloid areas
• Well-defined, no local invasion
• No enhancement in fat areas; soft tissue portions enhance
• Spontaneous hemorrhage in large lesions (>4 cm)
• Non-functional (incidentaloma), no treatment needed unless symptomatic

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Q4. Renal Cell Carcinoma (RCC) - Radiology

Definition

Radiology

Ultrasound

• Solid renal mass - variable echogenicity (often isoechoic or slightly hypoechoic to renal cortex; small tumors may be hyperechoic)
• Disruption of renal sinus fat
• Irregular margins; may show cystic areas (necrosis, hemorrhage)
• Color Doppler: Internal vascularity (arterial flow within mass); renal vein/IVC tumor thrombus
• Renal vein thrombus: echogenic material in renal vein/IVC
• Cystic RCC: Bosniak classification (see below)
• Limitations: Cannot stage disease, limited for <1 cm masses

CT (Modality of Choice for RCC)

• Iso- to hypodense mass relative to renal parenchyma
• Calcification (10-25%): coarse, irregular, or rim calcification
• Hemorrhagic or necrotic areas (high/low density)

• Clear cell RCC (most common type - 70%): Intense heterogeneous enhancement (most vascular of all subtypes; characteristic "enhancement followed by washout")
• Papillary RCC: mild, homogeneous enhancement
• Chromophobe RCC: moderate enhancement with spoke-wheel pattern

• Best for detecting renal masses - maximum contrast between tumor and parenchyma

• Filling defects in collecting system
• Hydronephrosis
• IVC thrombus assessment

MRI

• Superior to CT for: IVC/renal vein thrombus characterization (tumor thrombus vs bland thrombus), renal insufficiency, equivocal CT findings
• Clear cell RCC: T1 hypointense, T2 hyperintense; intense enhancement; chemical shift loss (intracellular lipid)
• Papillary RCC: T2 hypointense (iron hemosiderin), hypovascular
• MRI cardiac sequences: evaluate extent of IVC thrombus into right atrium

Bosniak Classification (Cystic RCC)

Nuclear Medicine

• DMSA/DTPA: Assesses differential renal function before nephrectomy
• PET-CT: FDG-avid in clear cell RCC; used for staging and follow-up

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Q5. Testicular Torsion - Radiology

Definition

Types

1. Intravaginal torsion (most common): within the tunica vaginalis; associated with "bell clapper deformity" (high insertion of tunica vaginalis)
2. Extravaginal torsion (neonates): entire testis and tunica twists

Clinical Presentation

• Sudden onset severe scrotal pain
• Nausea, vomiting
• High-riding testis with horizontal lie
• Absent cremasteric reflex (most reliable clinical sign)

Imaging Modality of Choice: Color Doppler Ultrasound

• Homogeneous medium echogenicity
• Epididymis: isoechoic to slightly hyperechoic
• Color Doppler: symmetrical blood flow bilaterally

• Testis may appear normal in early stages
• Epididymis enlarged, hypoechoic
• Color Doppler: Absent or markedly reduced intratesticular blood flow (hallmark finding)
• Comparison with contralateral testis is critical
• "Whirlpool sign": twisted spermatic cord seen on gray-scale/Doppler as a spiral or coil appearance - pathognomonic of torsion

• Testis: heterogeneous echogenicity (edema)
• Epididymis: enlarged, hyperechoic
• Reactive hydrocele
• Scrotal skin thickening

• Testis: markedly heterogeneous, hypoechoic (ischemic/infarcted)
• Irregular borders
• Absent Doppler flow within testis
• Paradoxical hyperemia in peritesticular tissues (reactive)
• Skin/scrotal wall thickening

• More sensitive than color Doppler for detecting low-velocity flow
• Helps distinguish partial torsion from complete

• Spiral or coil appearance of spermatic cord on transverse scanning
• High sensitivity (89%) and specificity (99%) for torsion
• Seen at the external inguinal ring

Scintigraphy (Tc-99m pertechnetate)

• Cold spot (photopenic area) on the affected side = reduced perfusion = torsion
• Hot spot = increased perfusion = epididymo-orchitis or missed torsion with hyperemia
• Less commonly used now; replaced by Color Doppler USG

MRI

• Not routinely used (too time-consuming in emergency)
• T2: low signal testis in infarction
• Can show loss of normal testicular zonal anatomy
• May help assess viability in subacute cases

Management Decision

• Doppler absent + clinical suspicion = IMMEDIATE surgical exploration (do not delay for imaging in high clinical suspicion)
• Testicular salvage rates: 90-100% if explored within 6 hours; <10% after 24 hours

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Q6. Wilms Tumor (Nephroblastoma)

Definition

Radiology

Ultrasound (First Line)

• Large, well-defined, predominantly solid intrarenal mass arising from one pole
• Echogenicity: heterogeneous (mixed solid and cystic components)
• Cystic areas due to necrosis, hemorrhage (common)
• Thin echogenic pseudocapsule
• Remaining kidney parenchyma compressed/displaced (intrinsic to kidney - differentiates from neuroblastoma which displaces kidney)
• Renal vein and IVC: Look for tumor thrombus (extends into IVC in 4-10%)
• Liver: assess for metastases (hepatic metastases are hypoechoic lesions)
• Nephrogenic rests (precursor lesions): bilateral hyperechoic cortical areas may be seen in Wilms tumor predisposition

CT (Staging and Surgical Planning)

• Heterogeneous mass, may contain fat, calcification (rare; suggests clear cell sarcoma if coarse)

• Large heterogeneous mass arising from and intrinsic to kidney
• Claw sign / beak of kidney wrapped around mass (confirms renal origin)
• Rim enhancement of pseudocapsule
• Areas of necrosis: non-enhancing low-density areas
• Functioning residual renal parenchyma enhances normally
• Contralateral kidney: Must be thoroughly evaluated (bilateral Wilms in 5-10%)
• IVC thrombus: Wilms tumor uniquely extends as bland thrombus in renal vein → IVC (differentiate from neuroblastoma which encases vessels)
• Lymphadenopathy: regional (para-aortic nodes)
• Lung: CT chest for pulmonary metastases (most common site)
• Liver metastases

MRI

• T1: hypointense heterogeneous mass
• T2: heterogeneous; cystic areas hyperintense; hemorrhage variable
• Gadolinium: enhancement pattern similar to CT
• Superior for IVC/renal vein thrombus extent, perirenal extension
• No radiation (ideal for pediatric patients and follow-up)

Comparison: Wilms vs. Neuroblastoma

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Q7. USG Findings in Any Three Common Scrotal Pathologies

1. Epididymo-orchitis

• Epididymis: Enlarged (>5 mm head), hypoechoic or heterogeneous epididymis
• Testis: Enlarged, hypoechoic (orchitis) - diffuse or focal
• Reactive hydrocele: Anechoic fluid collection between layers of tunica vaginalis
• Scrotal skin: Thickened (>8 mm)
• Color Doppler (KEY finding): Markedly increased blood flow (hyperemia) in epididymis and testis - "HYPERVASCULAR" pattern
  • Peak systolic velocity increased
  • Resistive index decreased (low resistance flow due to vasodilation)
• Pyocele: echogenic fluid/debris in hydrocele (pus)
• Abscess: hypoechoic/anechoic area within testis with surrounding hyperemia

• Orchitis: INCREASED flow; Torsion: ABSENT/REDUCED flow
• This Doppler distinction is the most critical differentiation

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2. Testicular Microlithiasis

• Bilateral multiple tiny hyperechoic foci (1-3 mm) scattered throughout testicular parenchyma
• No posterior acoustic shadowing (distinguishes from macrocalcifications)
• Classic criterion: ≥5 microliths per testicular cross-section
• Testis: may be normal size and echotexture
• No specific color Doppler findings

• Associated with TGCT (seminoma, non-seminomatous), cryptorchidism, infertility
• Annual USG surveillance recommended if additional risk factors (undescended testis, TGCT history, atrophic testis)

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3. Hydrocele

• Anechoic (black) fluid surrounding the testis on three sides (anterior, medial, lateral)
• Fluid between visceral and parietal layers of tunica vaginalis
• Posterior enhancement
• Testis and epididymis: usually normal
• Simple hydrocele: Clear anechoic fluid
• Complex hydrocele: Internal echoes (debris, fibrin strands, pus - pyocele, hemorrhage - hematocele)
• Hematocele: Echogenic acute blood → complex with septations (chronic)
• Wall: smooth, thin; thick/irregular wall suggests secondary cause

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Q8. Discuss Role of Radiology in Evaluation of Hematuria in Old Age Patient

Specific Considerations in Elderly Patients

• Most common cause of gross hematuria in patient >50 years: bladder cancer (urothelial carcinoma)
• Other common causes: BPH, prostate carcinoma, renal calculi, anticoagulant therapy
• Urothelial carcinoma (bladder, ureter, renal pelvis) is particularly common in elderly male smokers

Imaging Protocol for Elderly

1. KUB: Detect radio-opaque stones; assess for large prostatic calcification; look for calcified bladder wall (schistosomiasis)
2. USG Abdomen & Pelvis (First line):
   • Assess kidneys for masses, hydronephrosis, calculi
   • Bladder: intraluminal masses (sessile > papillary; broad base = more aggressive)
   • Bladder wall thickness (BWT): >3 mm when full suggests pathology
   • Prostate: BPH (enlarged, homogeneous, indenting bladder base); carcinoma (hypoechoic peripheral zone lesion on TRUS)
   • Post-void residual volume (PVR)
3. CT Urography (Investigation of Choice):
   • Three-phase CT (non-contrast, nephrographic, excretory)
   • Bladder tumors: sessile/pedunculated filling defect with enhancement
   • Renal masses: RCC (common cause of hematuria in elderly)
   • Upper tract TCC: filling defects in collecting system/ureter
   • Prostate: calcification, BPH, staging of Ca prostate
   • Limitation in elderly: Contrast nephropathy risk if pre-existing CKD (creatinine must be checked); may require MRU if GFR <30 ml/min/1.73m²
4. Cystoscopy: Mandatory in elderly patients with hematuria - detects flat CIS and small bladder tumors missed on all imaging
5. MR Urography: Alternative if contrast contraindicated (severe CKD, allergy)
   • MRI prostate (multiparametric): PI-RADS scoring if prostate cancer suspected
6. PET-CT: For staging of confirmed bladder/prostate malignancy
7. TRUS (Transrectal USG) + Biopsy: If PSA elevated + hypoechoic peripheral zone lesion

Key Radiological Findings Specific to Elderly:

• Bladder carcinoma: Sessile enhancing mass; focal wall thickening; papillary fronds (T2 high signal on MRI)
• BPH: Enlarged median lobe protruding into bladder (intravesical BPH); "J-sign" ureter elevation on IVU
• Prostate carcinoma (on MRI): T2 hypointense lesion in peripheral zone; restricted diffusion on DWI; early enhancement on DCE
• Renal calculi: Radio-opaque on plain film; hyperechoic with shadowing on USG; high density (800-2000 HU) on non-contrast CT

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Q9. Hypertrophic Pyloric Stenosis (HPS)

Definition

Imaging Modality of Choice: Ultrasound

• Target sign (transverse view): Thick hypoechoic muscle ring surrounding central echogenic mucosa - classic "bull's eye" or "donut" appearance
• Cervix sign (longitudinal view): Elongated pyloric channel projects into fluid-filled stomach like a cervix into a uterus
• Antrum/Stomach: Distended fluid-filled stomach with vigorous peristaltic waves
• Non-passage of fluid: Failure of fluid (formula/water) to pass through pylorus into duodenum during real-time observation
• String sign on USG: Thin streak of compressed lumen visible as echogenic line
• Pyloric muscle: hypoechoic (muscle)
• Mucosa: hyperechoic (mucosa and submucosa)

• String sign: Thin elongated pyloric channel (contrast squeezed through narrow lumen)
• Double-track sign: Two parallel lines of contrast in the pyloric channel (mucosal folds)
• Beak/Shoulder sign (Kirklin's sign): Shouldering effect at junction of antrum and pylorus
• Caterpillar stomach: Visible peristaltic waves on fluoroscopy
• Delayed gastric emptying
• Stomach: dilated

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Q10. Ureterocele

Definition

Types

1. Orthotopic (Intravesical/Simple) ureterocele: Located at normal ureteric orifice; usually in adults; associated with single system; often asymptomatic
2. Ectopic ureterocele: Located medial/inferior to normal orifice; associated with upper pole moiety of duplex system; common in children; may prolapse

Radiology

Ultrasound (Most Important Modality)

• Thin-walled, anechoic cystic structure at the trigone/base of bladder near ureteric orifice
• Appears as a cyst within the bladder on transverse scan
• "Cobra head" sign: The dilated ureter with its thin wall is surrounded by a halo of bladder wall, resembling a cobra's hood
• Associated findings:
  • Upper pole hydronephrosis (in duplex system)
  • Upper moiety hydroureter (dilated tortuous ureter)
  • Ipsilateral upper pole is often dysplastic/non-functioning
  • Contralateral VUR (secondary to displacement of trigone)
• Color Doppler: ureteric jet from the ureterocele can be seen

IVU / CT Urography

• Cobra head sign (most classic): Radiolucent halo around contrast-filled ureterocele with opacified bladder - rim of contrast around the cystic ureterocele
• "Drooping lily" sign: In duplex system, the non-functioning upper pole (hydronephrotic) displaces the functioning lower pole downward, causing the lower pole calyces to point laterally and downward - resembling a drooping lily
• Upper pole moiety: dilated/hydronephrotic pelvicalyceal system
• Upper pole ureter: tortuous, dilated, coursing medially (Weigert-Meyer rule: upper pole ureter inserts ectopically below and medial to lower pole ureter)
• Lower pole: may show VUR or hydronephrosis

Voiding Cystourethrogram (VCUG)

• Filling defect at bladder base (ureterocele visible)
• VUR into ipsilateral lower pole or contralateral ureter
• May show prolapse into urethra in girls (causing obstruction)
• Eversion of ureterocele on voiding films

DMSA Renal Scan

• Assesses differential function: upper pole moiety is often poorly functional
• Essential for surgical planning (upper pole heminephrectomy vs. endoscopic incision)

Weigert-Meyer Rule

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Q11. Embryology of Kidney - Congenital Anomalies - Pediatric Renal Solid Occupying Lesions

Embryology of Kidney

1. Pronephros (Week 3-4): Rudimentary, non-functional; immediately degenerates
2. Mesonephros (Week 4-8): Functional for a brief period; forms Wolffian (mesonephric) duct; largely regresses
3. Metanephros (Week 5 onwards): Permanent kidney

• Ureteric bud (outgrowth of Wolffian duct) → induces metanephric blastema → branches repeatedly → forms collecting system (ureter, renal pelvis, major & minor calyces, collecting ducts)
• Metanephric blastema (induced by ureteric bud) → forms nephrons (glomerulus, PCT, loop of Henle, DCT)

• Week 5-6: Metanephros begins formation
• Week 6-9: Kidney ascends from pelvis to lumbar region (L1-L2)
• Ascent driven by: differential growth of embryo, decrease in body curvature, differential cell growth
• Rotation: kidneys rotate 90° medially during ascent (pelvis faces anteriorly → medially)
• Blood supply changes during ascent (original pelvic arteries regress; new vessels from aorta develop)
• Week 10-12: Kidneys become functional, fetal urine contributes to amniotic fluid

• Failure of ureteric bud formation → Renal agenesis
• Failure of induction → Renal dysplasia/MCDK
• Failure of ascent → Pelvic kidney
• Failure of rotation → Malrotation
• Abnormal fusion → Horseshoe kidney
• Incomplete ureteric bud branching → Duplex system

Congenital Anomalies of Kidney (Classification - same as Q2)

Pediatric Renal Solid Occupying Lesions

Classification:

• Nephroblastomatosis (nephrogenic rests)
• Mesoblastic nephroma (most common solid renal tumor in neonate)
• Multilocular cystic nephroma
• Oncocytoma
• Angiomyolipoma (rare in children; associated with TSC)

• Wilms tumor/Nephroblastoma (most common)
• Clear cell sarcoma of kidney (CCSK) - "bone-metastasizing renal tumor of childhood"
• Rhabdoid tumor of kidney (RTK) - most aggressive; associated with brain metastases and SMARCB1 mutation
• Renal cell carcinoma (rare; adolescents; associated with Xp11 translocation)
• Neuroblastoma (adrenal/retroperitoneal - see Q6 distinction)

Radioimaging Features:

• Precursor lesions to Wilms tumor
• USG: Bilateral hyperechoic cortical lesions; may be difficult to distinguish from Wilms
• CT: Multiple bilateral renal masses; lenticular peripheral lesions with uniform enhancement
• MRI: T2 hypointense peripheral lesions (distinguishes from Wilms - T2 hyperintense)

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Q12. Imaging and Color Doppler Findings in Acute Scrotum

Definition

Causes of Acute Scrotum

1. Testicular torsion (surgical emergency)
2. Torsion of testicular appendage (appendix testis)
3. Epididymo-orchitis (most common in adults)
4. Trauma / hematocele
5. Incarcerated inguinal hernia
6. Fournier's gangrene
7. Idiopathic scrotal edema

Imaging Modality: High-Frequency USG (7.5-15 MHz) with Color Doppler

Imaging Findings:

1. Testicular Torsion

• Gray-scale: Enlarged, hypoechoic, heterogeneous testis; reactive hydrocele; scrotal wall thickening
• Color Doppler: Absent intratesticular flow (vs. contralateral)
• Whirlpool sign: Pathognomonic - twisted spermatic cord
• Spiral/coil sign of cord: Twisting of cord at inguinal ring

2. Torsion of Appendix Testis (Appendix Torsion)

• Gray-scale: Small hyperechoic or heterogeneous extratesticular nodule near upper pole of testis (2-5 mm)
• Reactive hydrocele
• Normal testis and epididymis
• Scrotal skin thickening
• "Blue dot sign" - clinical sign (visible through thin scrotal skin in children)
• Color Doppler: Normal or increased perinodular flow; testicular blood flow is NORMAL (distinguishes from torsion)
• Management: Conservative (NSAIDs); self-limiting within 5-7 days

3. Epididymo-Orchitis

• Gray-scale: Enlarged, hypoechoic epididymis; enlarged hypoechoic testis; reactive hydrocele
• Color Doppler: Markedly INCREASED blood flow (hyperemia) - key feature
• Pyocele: echogenic debris in hydrocele
• Abscess: focal hypoechoic area, loss of normal architecture, surrounding rim of hyperemia

4. Scrotal Trauma / Hematocele

• Gray-scale:
  • Hydrocele with internal echoes (hematocele - acute blood = homogeneous echogenicity; chronic = heterogeneous with septations)
  • Testicular fracture: linear hypoechoic defect through parenchyma
  • Testicular contusion: focal heterogeneous area
  • Intratesticular hematoma: focal hyperechoic (acute) → complex (subacute)
• Color Doppler:
  • Testicular fracture: absent flow across fracture line
  • Contusion: normal or reduced flow
  • Large hematocele: compresses testis reducing flow
• Tunica albuginea breach (rupture): Extruded testicular tissue through disrupted tunica; absent normal testicular border; hemorrhagic content
• CT: better for complex trauma to assess associated pelvic injuries

5. Fournier's Gangrene

• Necrotizing fasciitis of perineum/scrotum
• USG: Scrotal wall thickening; hyperechoic foci with dirty shadowing (subcutaneous gas)
• Testes often normal (blood supply from testicular artery - separate from fascial supply)
• CT: Subcutaneous gas (emphysema) tracking along fascial planes; fascial thickening; perineal involvement

Summary Table - Acute Scrotum Differentiation

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Q13. MRI Findings for Adnexal Lesions

Definition

MRI Technique

• T1-weighted (T1W): distinguishes fat, blood, protein
• T2-weighted (T2W): ovarian tissue characterization; fluid
• Fat saturation sequences: confirm fat content
• Diffusion-weighted imaging (DWI): restricted diffusion = malignancy
• Gadolinium (DCE-MRI): pattern and degree of enhancement

Benign Adnexal Lesions

1. Functional/Simple Ovarian Cyst

• T1: Hypointense (fluid signal)
• T2: Markedly hyperintense (water)
• Post-contrast: No enhancement
• Thin wall (<3 mm), no septations, no solid components
• Resolves on follow-up

2. Mature Cystic Teratoma (Dermoid Cyst)

• Most common ovarian tumor in reproductive age
• T1: Hyperintense (fat - bright); chemical shift artifact (India ink artifact at fat-fluid interface)
• T2: Hyperintense fat; Rokitansky's protuberance (dermoid plug) - soft tissue nodule projecting into cyst
• Fat suppression sequences: Signal drops in fat-containing areas (confirms fat)
• Chemical shift MRI: signal cancellation at fat-water interfaces
• Calcification: low signal on all sequences
• Floating sebaceous material: diffuse T1 high signal
• Danger signs for malignant transformation (1-2%): Solid component with enhancement, rapid growth

3. Endometrioma

• T1: Markedly HYPERINTENSE (chronic hemorrhage = blood products T1-shortening effect) - "bright T1"
• T2: Hypointense (T2 "shading" - layering of different age blood products) - classic finding
• T2 shading sign: Gradual darkening from superior to inferior within cyst = pathognomonic of endometrioma
• No solid enhancing component
• May be bilateral; may have multiple cysts ("chocolate cysts")
• Associated with distortion of anatomy (endometriosis - hypointense T2 lesions in peritoneum, POD)

4. Ovarian Fibroma/Fibrothecoma

• Solid ovarian mass
• T1: Hypointense
• T2: Markedly HYPOINTENSE (fibrous stroma with low water content) - key feature differentiating from other solid tumors
• Minimal enhancement
• Meigs syndrome: fibroma + ascites + right-sided pleural effusion

5. Hydrosalpinx / Pyosalpinx

• Dilated fallopian tube
• T2: Tortuous, tubular, fluid-filled structure separate from ovary
• Hydrosalpinx: Simple fluid signal (T2 bright, T1 dark); "incomplete septations" - mucosal folds producing incomplete transverse folds
• Pyosalpinx: Complex content (T1 intermediate, T2 intermediate); wall thickening; enhancement; free fluid

Malignant Adnexal Lesions

6. Epithelial Ovarian Carcinoma (Serous/Mucinous Cystadenocarcinoma)

• T2: Complex cystic-solid mass; thick irregular septa (>3 mm); papillary projections (T2 intermediate signal, enhance with contrast)
• T1: Variable; hemorrhagic fluid may be T1 hyperintense
• Post-gadolinium: Solid components and septations enhance (key malignancy feature)
• DWI: Solid components show restricted diffusion (ADC <1.0 × 10⁻³ mm²/s)
• Staging features on MRI:
  • Peritoneal deposits: T2 intermediate nodules on peritoneal surfaces
  • Omental cake: T2 intermediate, enhancing thickening of omentum
  • Ascites: T2 bright free fluid
  • Lymphadenopathy (>1 cm short axis)
  • Liver surface deposits vs. parenchymal metastases

7. Borderline Serous Tumor

• T2: multilocular cystic mass with fine septations and papillary projections
• Less aggressive than carcinoma; limited enhancement

8. Mucinous Cystadenoma / Cystadenocarcinoma

• Multilocular cystic mass ("stained glass" appearance)
• T1: Variable signal in different locules (different mucinous content concentrations)
• T2: Variable (high for watery mucin, low for thick mucin)
• Malignant: papillary projections, solid components, peritoneal implants

9. Tubo-Ovarian Abscess (TOA)

• Complex adnexal mass
• T2: Thick-walled cystic structure with internal debris; tube and ovary merged into one complex mass
• T1: Low to intermediate signal with high signal areas (hemorrhage/protein)
• DWI: Restricted diffusion in abscess (high signal)
• Enhancement: thick wall and septa enhance

ADNEX MRI Features Suggesting Malignancy:

1. Solid components with enhancement
2. Thick irregular septa (>3 mm)
3. Papillary projections
4. Restricted diffusion (ADC value <1.0 × 10⁻³)
5. Peritoneal/omental deposits
6. Ascites
7. Lymphadenopathy
8. Necrosis within solid areas

O-RADS MRI Classification (Ovarian-Adnexal Reporting and Data System):

• O-RADS 1: Normal ovary
• O-RADS 2: Almost certainly benign (<1% malignancy)
• O-RADS 3: Low risk (1-10%)
• O-RADS 4: Intermediate risk (10-50%)
• O-RADS 5: High risk (>50% malignancy)

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Q14. Draw Cut Section of Kidney + Role of USG in Case of Painless Hematuria

Cut Section of Kidney

1. Fibrous capsule
2. Renal cortex (outer, 1-1.5 cm)
3. Columns of Bertin (cortical extensions between pyramids)
4. Medullary pyramids (8-18 pyramids)
5. Renal papilla (apex of pyramid → minor calyx)
6. Minor calyces
7. Major calyces (2-3)
8. Renal pelvis
9. Ureteropelvic junction (UPJ) → Ureter
10. Renal sinus (fat, vessels, lymphatics)
11. Medullary rays
12. Arcuate vessels (at corticomedullary junction)

Role of USG in Painless Hematuria

• Painless hematuria is a red flag symptom - suggests malignancy until proven otherwise
• Most common cause in patients >50 years: Bladder carcinoma (urothelial carcinoma)
• Other causes: RCC, upper tract TCC, AVM, bleeding disorder, IgA nephropathy (microscopic)

USG Protocol for Painless Hematuria

• Full bladder (250-300 ml): best for bladder evaluation
• Convex probe (3.5-5 MHz): general abdominal scan
• Linear probe (7-15 MHz): superficial structures, kidneys in thin patients

USG Findings in Causes of Painless Hematuria:

• Sessile or polypoid echogenic mass projecting into bladder lumen
• Disruption of smooth bladder wall (focal wall thickening)
• Broad base = sessile = higher stage (muscle invasion)
• Papillary = pedunculated = lower stage (superficial)
• Color Doppler: internal vascularity (distinguishes tumor from blood clot - clot has no flow)
• Assessment: bladder wall thickness, extension into adjacent fat
• Limitation: Cannot detect flat CIS, lesions at bladder neck/dome, lesions <5 mm

• Solid renal mass: variable echogenicity
• Color Doppler: internal arterial flow
• Renal vein: tumor thrombus (echogenic material)
• IVC: extension of thrombus
• Contralateral kidney: normal

• Highly echogenic well-defined intrarenal mass (fat content)

• 1.5 cm lesions: posterior shadowing

• Color Doppler: internal vascularity (especially if large)
• Key distinction from RCC: hyperechoic on USG; confirmed with CT (fat density <-30 HU)

• Hyperechoic foci with posterior acoustic shadowing
• Hydronephrosis if obstructing
• Ureteric calculus: difficult to see directly, but look for hydronephrosis + twinkling artifact on Doppler

• Upper pole hydronephrosis (obstruction by TCC)
• Echogenic filling defect in dilated renal pelvis
• Limited detection of ureteric tumors

• Complex cyst: echogenic fluid, thin wall, no vascularity on Doppler
• Thick wall / septations / solid nodule → Bosniak III/IV → suspicious

• Bilateral enlarged kidneys with multiple cysts
• May present with hematuria due to cyst hemorrhage or calculi

Limitations of USG in Painless Hematuria:

• Cannot reliably detect flat urothelial lesions (CIS)
• Limited sensitivity for ureteric tumors (14%)
• Limited for small papillary bladder tumors (<5 mm)
• Cannot provide adequate staging information
• Operator and body habitus dependent

When USG is Negative in Painless Hematuria:

• Proceed to CT Urography (gold standard - sensitivity 94% for upper tract TCC)
• Cystoscopy mandatory (USG cannot exclude bladder malignancy)
• Urine cytology for atypical/malignant cells

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Summary of All Answers

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Quick Reference - All 14 Answers (Already Written Above)

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Q13. MRI Findings for Adnexal Lesions

Definition

MRI Technique

• T1W (T1-weighted): Identifies fat, blood, protein-rich fluid
• T2W (T2-weighted): Best for morphology, fluid characterization, ovarian stroma
• Fat suppression (STIR/Dixon/ChemSat): Confirms fat content (signal drops = fat)
• DWI (Diffusion-weighted imaging): Restricted diffusion (high signal DWI, low ADC) = malignancy
• DCE-MRI (Dynamic contrast-enhanced): Pattern, degree, and timing of enhancement
• Chemical shift MRI: Confirms intracellular fat (out-of-phase signal drop)

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BENIGN ADNEXAL LESIONS

1. Simple Ovarian Cyst / Functional Cyst

• T1W: Hypointense (simple fluid - dark)
• T2W: Markedly hyperintense (water - bright)
• Post-contrast: No wall or internal enhancement
• Features: Thin wall (<3 mm), no septations, no solid components, no restricted diffusion
• Resolves spontaneously within 1-2 cycles
• O-RADS MRI 2: Almost certainly benign

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2. Mature Cystic Teratoma (Dermoid Cyst)

• Most common ovarian tumor in reproductive age women (20-40 yrs)
• T1W: Markedly HYPERINTENSE (fat content - the brightest adnexal lesion on T1)
• T2W: Hyperintense fat component; Rokitansky protuberance (dermoid plug) appears as a solid nodule projecting into the cyst interior
• Fat suppression: Signal drops dramatically in fat areas - confirmatory finding
• Chemical shift (in-phase/out-of-phase): India ink artifact at fat-fluid interface (signal cancellation on out-of-phase = black rim)
• Calcification (teeth, bone): low signal on all sequences
• Sebaceous fluid: diffuse T1 high signal filling cyst
• Mature hair: low signal linear structures within fat
• Malignant transformation (1-2%): Enhancing solid component, rapid growth, local invasion

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3. Endometrioma ("Chocolate Cyst")

• Ovarian cyst containing old menstrual blood (chronic hemorrhage)
• T1W: Markedly HYPERINTENSE (T1 bright - blood products shortening T1 relaxation) - classic "bright T1"
• T2W: HYPOINTENSE with "T2 shading" - the hallmark finding
  • T2 shading sign: gradual darkening from superior to inferior within cyst due to layering of different-aged blood products (deoxyhaemoglobin, methemoglobin)
  • Pathognomonic of endometrioma
• Post-contrast: No solid enhancing component (wall may mildly enhance)
• DWI: No restricted diffusion (unlike malignancy)
• May be bilateral; multiple "kissing ovaries" (bilateral endometriomas adherent in POD)
• Associated peritoneal endometriosis: T2 hypointense nodules on peritoneal surfaces, uterosacral ligaments, POD
• Distinction from hemorrhagic functional cyst: T2 shading + T1 bright + no resolution on follow-up = endometrioma

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4. Ovarian Fibroma / Fibrothecoma

• Solid ovarian stromal tumor (sex cord-stromal origin)
• T1W: Hypointense (low signal - similar to muscle)
• T2W: Markedly HYPOINTENSE (very dark - key distinguishing feature due to dense fibrous stroma with low free water)
• Post-contrast: Minimal, gradual enhancement (fibrous tissue enhances slowly)
• DWI: May show mild restriction but ADC not as low as malignancy
• Well-defined, smooth margins; homogeneous
• Meigs Syndrome: Ovarian fibroma + ascites + right-sided pleural effusion (benign; resolves after tumor removal)
• Fibrothecoma: intermediate T2 signal (contains more cellular thecomatous elements)

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5. Hydrosalpinx / Pyosalpinx

• T2W: Tubular, tortuous, folded C-shaped or S-shaped fluid-filled structure separate from ovary
• T1W: Hypointense (simple fluid)
• "Incomplete septations" - longitudinal mucosal folds create partial transverse folds on cross-section ("cogwheel" appearance on T2)
• No mural nodules, no enhancement
• Ipsilateral ovary identifiable separately

• T1W: Intermediate to high signal (protein-rich fluid)
• T2W: Intermediate signal with thick walls
• Post-contrast: thick enhancing wall
• DWI: restricted diffusion within lumen (high signal)
• Associated free pelvic fluid

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6. Peritoneal Inclusion Cyst

• Seen in women with prior surgery/pelvic inflammatory disease
• Fluid trapped around normal ovary by adhesions
• T2W: Loculated fluid conforming to pelvic structures, surrounding normal ovary ("spider web" appearance)
• T1W: Hypointense
• Normal ovary visible within the collection
• No thick septa, no solid components

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MALIGNANT ADNEXAL LESIONS

7. Epithelial Ovarian Carcinoma (Serous / Mucinous Cystadenocarcinoma)

• Most common ovarian malignancy; peak 50-70 yrs
• T2W: Complex cystic-solid mass; irregular thick septa (>3 mm); papillary projections (T2 intermediate signal); solid mural nodules
• T1W: Variable; hemorrhagic components may be T1 hyperintense
• Post-gadolinium: Solid components, papillary projections, and thick septations enhance - the key malignancy indicator
• DWI: Solid components show restricted diffusion; ADC value <1.0 × 10⁻³ mm²/s
• Staging findings on MRI:

• Peritoneal carcinomatosis: T2 intermediate enhancing nodules on peritoneum, omentum, bowel serosa
• Omental cake: Diffuse T2 intermediate thickening of omentum with enhancement
• Ascites: T2 bright free fluid in peritoneal cavity
• Lymphadenopathy: short axis >1 cm (para-aortic, pelvic nodes)

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8. Borderline Serous Tumor (Low Malignant Potential)

• T2W: Multilocular cystic mass with fine septations + papillary projections (smaller than in carcinoma)
• Enhancement of papillary projections (mild to moderate)
• No restricted diffusion typically
• No peritoneal implants (usually Stage I)

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9. Mucinous Cystadenoma / Cystadenocarcinoma

• Multilocular cystic mass - classically >10 locules ("stained glass" or "honeycomb" appearance)
• T1W: Variable signal in different locules (different mucinous concentrations - "signal stacking")
  • Some locules T1 bright (thick mucin), others T1 dark (watery mucin)
• T2W: Variable - high signal for watery mucin, intermediate/low for thick viscous mucin
• Malignant features: papillary projections, enhancing solid components, wall thickening

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10. Tubo-Ovarian Abscess (TOA)

• Complex inflammatory mass merging tube and ovary
• T2W: Thick-walled cystic/complex mass; internal debris; loss of normal ovarian/tubal anatomy
• T1W: Low to intermediate signal; high T1 areas = hemorrhage or protein
• DWI: Restricted diffusion within abscess (high DWI signal, low ADC) - distinguishes pus from other fluid
• Post-contrast: Thick enhancing walls and septa; surrounding fat stranding (T2 bright fat signal = edema)
• Associated free pelvic fluid
• Gas within lesion (rare but diagnostic of abscess)

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MRI Features That Suggest Malignancy (ADNEX MRI Criteria)

1. Solid enhancing components
2. Thick irregular septa (>3 mm) with enhancement
3. Papillary projections
4. Restricted diffusion in solid areas (ADC <1.0 × 10⁻³ mm²/s)
5. Peritoneal/omental deposits
6. Ascites
7. Lymphadenopathy (>1 cm)
8. Necrosis within solid components
9. Bilateral ovarian involvement (suggests metastatic/Krukenberg)

O-RADS MRI Classification

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Q14. Draw the Cut Section of Kidney. Describe the Role of USG in Case of Painless Hematuria

Part A: Cut Section of Kidney

         ┌─────────────────────────────────────────┐
         │         FIBROUS CAPSULE (outer layer)   │
         │   ┌─────────────────────────────────┐   │
         │   │   CORTEX  (1.0 - 1.5 cm thick)  │   │
         │   │  • Renal corpuscles (glomeruli)  │   │
         │   │  • PCT, DCT                      │   │
         │   │  • Columns of Bertin ─────────┐  │   │
         │   │    (cortex dipping between     │  │   │
         │   │     medullary pyramids)        │  │   │
         │   ├────────────┬─────┬─────────────┤  │   │
         │   │  PYRAMID 1 │     │  PYRAMID 2  │  │   │
         │   │ (medulla)  │SINUS│  (medulla)  │  │   │
         │   │            │     │             │  │   │
         │   │  ↓ papilla │     │ papilla ↓   │  │   │
         │   │ Minor calyx│     │ Minor calyx │  │   │
         │   │     ↓      │     │     ↓       │  │   │
         │   │  Major calyx ←───→ Major calyx │  │   │
         │   │         ↓                      │  │   │
         │   │      RENAL PELVIS              │  │   │
         │   │         ↓                      │  │   │
         │   │       URETER (UPJ)             │  │   │
         │   └────────────────────────────────┘  │   │
         └─────────────────────────────────────────┘

Labeled Structures of the Cut Section:

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Part B: Role of USG in Painless Hematuria

Significance of Painless Hematuria

• Bladder carcinoma (most common cause of gross painless hematuria in patients >50 years)
• Renal cell carcinoma (RCC)
• Urothelial carcinoma (renal pelvis, ureter)
• Angiomyolipoma (AML)
• IgA nephropathy (microscopic hematuria, young patients)

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USG Technique

• Probe: Curved array 3.5-5 MHz (abdomen); Linear 7-15 MHz (superficial structures)
• Bladder must be full (250-300 ml) for optimal evaluation
• Scan: Both kidneys in longitudinal and transverse planes; bladder in two planes; post-void residual

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USG Findings in Causes of Painless Hematuria

1. Bladder Carcinoma (Urothelial Carcinoma) - Most Important

• Echogenic mass projecting into the bladder lumen from the wall
• Papillary (polypoid): Pedunculated, frond-like echogenic mass; lower stage (superficial lamina propria)
• Sessile (flat/broad base): Focal wall thickening; higher stage (suggests muscle invasion)
• Bladder wall thickness >5 mm at the site of lesion
• Color Doppler: internal vascularity within the mass - distinguishes tumor from blood clot (clot = NO internal flow)
• Post-void: tumor remains fixed; clot may shift position
• Location: trigone and posterior wall most common; lateral walls and dome less common
• Large tumors: invasion into perivesical fat (irregular outer bladder contour)
• Limitation: Cannot detect flat carcinoma in situ (CIS), lesions <5 mm, lesions at dome/bladder neck

2. Renal Cell Carcinoma (RCC)

• Solid intrarenal mass: Variable echogenicity
  • Small RCC (<3 cm): often hyperechoic (similar to AML - requires CT differentiation)
  • Larger RCC: heterogeneous, iso- or hypoechoic; irregular margins
• Disruption of renal sinus fat (invasion)
• Cystic areas within mass: necrosis, hemorrhage
• Renal vein: Echogenic solid material = tumor thrombus (critical finding)
• IVC: Thrombus extending up to hepatic veins or right atrium
• Color Doppler: Internal arterial waveform within mass (tumor vascularity); distinguishes from simple cyst; renal vein patency
• Adrenal gland: Ipsilateral adrenal metastasis (separate mass above kidney)

3. Angiomyolipoma (AML)

• Highly echogenic (bright) well-defined intrarenal mass - characteristic appearance
• Fat content causes high echogenicity (similar to or brighter than renal sinus fat)
• Posterior acoustic shadowing in lesions >1.5 cm
• Well-defined margins; round or oval
• Color Doppler: internal vascularity (particularly in large AML - risk of spontaneous hemorrhage if >4 cm)
• Critical distinction from RCC: Both can be hyperechoic on USG; CT confirms fat density (<-30 HU) in AML
• Bilateral multiple AMLs: associated with tuberous sclerosis complex (TSC)

4. Renal Calculi

• Hyperechoic foci with posterior acoustic shadowing within renal parenchyma or collecting system
• Twinkling artifact on color Doppler: rapid color change behind stone = highly specific for calculi
• Obstructing stone: hydronephrosis (dilated pelvicalyceal system, dilated ureter)
• Ureteric stone: difficult to visualize directly; secondary hydronephrosis suggests obstruction
• Staghorn calculus: large echogenic cast of the renal pelvis + all calyces

5. Transitional Cell Carcinoma (TCC) of Renal Pelvis

• Echogenic non-shadowing soft tissue filling defect within dilated renal pelvis
• Hydronephrosis proximal to the lesion
• Color Doppler: internal vascularity distinguishes TCC from blood clot (avascular)
• Lower pole cortical thinning with preserved sinus (unlike RCC which replaces parenchyma)
• USG has very limited sensitivity for ureteric TCC (only 14%); CT Urography required

6. Hemorrhagic Renal Cyst

• Complex cyst with internal echoes (blood products)
• Thin wall; no Doppler flow within (distinguishes from cystic RCC which has flow in solid components)
• Thick wall / mural nodule / enhancing solid areas → Bosniak III or IV → suspicious for cystic RCC
• Simple hemorrhagic cyst: follow-up with USG or CT

7. Arteriovenous Malformation (AVM) / Renal AV Fistula

• Cause of hematuria without visible mass
• Gray-scale: May appear as small hypoechoic area or tubular structure
• Color Doppler: Focal area of intense color (mosaic pattern) due to turbulent high-velocity flow
• Pulsed wave Doppler: arterial waveform in a venous structure (arterialization of venous flow) = AV fistula
• Peak systolic velocity markedly elevated
• Confirms vascular etiology; refer for DSA and possible embolization

8. Polycystic Kidney Disease (ADPKD)

• Bilateral enlarged kidneys with multiple cysts of varying sizes
• Hematuria due to cyst hemorrhage or associated renal calculi
• Complex cysts (heterogeneous, echogenic content): intracystic hemorrhage
• Liver cysts often co-exist

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Algorithm: USG Approach to Painless Hematuria

PAINLESS HEMATURIA
        ↓
Full bladder USG + Both kidneys
        ↓
 ┌──────────────────────────┬──────────────────────────┐
 │    POSITIVE FINDING      │     NEGATIVE FINDING     │
 ↓                          ↓                          ↓
Bladder mass               Renal mass             Proceed to:
→ CT staging               → CT characterization   • CT Urography
Renal stone                Hydronephrosis          • Cystoscopy
→ NCCT abdomen             → CTU/IVU               • Urine cytology
AML/RCC → CT
        ↓
Color Doppler:
• Flow in mass = tumor (not clot)
• Absent renal vein flow = thrombus
• Mosaic pattern = AVM

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Limitations of USG in Painless Hematuria

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When to Proceed Beyond USG

Key principle: A negative USG does NOT exclude bladder malignancy. Cystoscopy is always required when clinical suspicion is high, regardless of imaging findings. CT Urography remains the gold standard for complete upper and lower urinary tract evaluation in hematuria.