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RADIOLOGY - FULL ANSWERS

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1. Hematuria: Role of Radiology (20 Marks)

Definition

Classification

• Gross/Frank hematuria - visible to naked eye
• Microscopic hematuria - detected on dipstick or microscopy
• Glomerular hematuria - dysmorphic RBCs, RBC casts (renal parenchymal disease)
• Non-glomerular hematuria - isomorphic RBCs (urothelial/urological cause)

Causes

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Radiological Investigation Algorithm

Step 1 - Urine Analysis and Cytology

Step 2 - Ultrasound (USG) - FIRST LINE

• No radiation
• Widely available, inexpensive
• Real-time assessment

• Renal calculi - Hyperechoic foci with posterior acoustic shadowing
• Renal masses - Solid vs cystic (Bosniak classification for cystic lesions)
• Hydronephrosis - Dilated pelvicalyceal system suggesting obstruction
• Bladder tumors - Echogenic masses projecting into lumen; best seen with full bladder
• Bladder calculi - Hyperechoic with posterior shadowing, mobile
• Prostatic enlargement - BPH; may show median lobe protrusion into bladder
• Polycystic kidney - Multiple bilateral cysts replacing renal parenchyma
• Renal vein thrombosis - Loss of venous flow on Doppler

• Renal artery stenosis - Increased peak systolic velocity (>180 cm/s)
• Renal vein thrombosis - Absent venous signal
• AV malformation - Turbulent flow on color Doppler
• Tumor vascularity - Neovascularity in RCC

Step 3 - CT Urography (CTU) - GOLD STANDARD

• Detects calculi (hyperdense)
• Baseline density of lesions
• Identifies calcifications in tumors

• Cortical enhancement
• Renal artery/vein assessment
• Detects hypervascular tumors (RCC is hypervascular)

• Best for detecting parenchymal lesions
• Filling defects in collecting system
• Urothelial tumors

• Opacification of calyces, renal pelvis, ureter, bladder
• Filling defects from TCC
• Ureteral irregularities

• RCC - Heterogeneous enhancing mass, often with central necrosis; hypervascular in arterial phase
• TCC of renal pelvis - Soft tissue filling defect in collecting system, moderate enhancement
• Ureteral TCC - Filling defect, "goblet sign" (dilatation of ureter below tumor)
• Bladder TCC - Sessile or papillary mass, wall thickening
• Calculi - Hyperdense on NCCT
• Renal infarction - Wedge-shaped area of non-enhancement (cortical rim sign may be present)
• Renal trauma - Lacerations, perirenal hematoma, collecting system injuries
• Papillary necrosis - "Lobster claw" or "egg in cup" appearance
• Medullary sponge kidney - Nephrocalcinosis, paintbrush calyceal blush

Step 4 - MRI Urography

• Radiation avoidance needed (young patients, pregnancy)
• CT contrast contraindicated (renal failure)
• Iodine allergy
• Equivocal CT findings

• T2WI: Cysts are hyperintense, solid masses intermediate
• T1WI+Gd: Enhancement characterizes malignant lesions
• DWI: Restricted diffusion in malignant tumors
• MR angiography: Vascular lesions, AV malformations

Step 5 - Intravenous Urography (IVU/IVP)

• Filling defects in collecting system
• Ureteral deviation
• "Phantom calyx" in TCC of upper pole
• Obstructive uropathy

Step 6 - Retrograde Pyelography (RGP)

• IVU/CTU shows incomplete opacification
• Combined with ureteroscopy
• Maps upper tract TCC extent

• Irregular filling defects (TCC)
• "Bergman's coil sign" - catheter coils below ureteral TCC due to soft obstruction

Step 7 - Cystography

• Bladder trauma assessment
• Filling defects in bladder
• Bladder rupture (extravasation of contrast)

Step 8 - Angiography / Intervention

• AV malformation/fistula
• Post-traumatic bleeding
• Severe refractory hematuria
• Pre-surgical embolization of RCC

• AVM - tangled vascular nidus, early venous filling
• Pseudoaneurysm - localized saccular outpouching
• Renal artery aneurysm

Step 9 - Nuclear Medicine

• DMSA scan - Renal cortical scarring, differential function
• DTPA/MAG3 - Obstructive uropathy, split renal function
• Bone scan - Metastatic workup in malignancy

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Bosniak Classification (for Cystic Renal Masses)

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Hematuria in Specific Situations

• Calculi (most common cause)
• Clot colic (TCC)
• Pyelonephritis
• Renal infarction

• Bladder TCC (most sinister cause in adults >40 years)
• RCC
• TCC of upper tract
• Glomerulonephritis

• CT with contrast - standard of care
• AAST grading of renal trauma (Grades I-V)

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2. Cut Section of Kidney + Congenital Anomalies of Urinary System + Three Renal Anomalies in Detail

Cut Section of Kidney (Diagram Description)

        KIDNEY - CORONAL CUT SECTION
        
    ┌─────────────────────────────────┐
    │     Fibrous Capsule             │
    │  ┌───────────────────────────┐  │
    │  │      CORTEX               │  │
    │  │   (Columns of Bertin)     │  │
    │  │  ┌─────────────────────┐  │  │
    │  │  │   MEDULLA           │  │  │
    │  │  │  (Pyramids)         │  │  │
    │  │  │   ┌─────────────┐   │  │  │
    │  │  │   │  MINOR      │   │  │  │
    │  │  │   │  CALYX      │   │  │  │
    │  │  │   └──────┬──────┘   │  │  │
    │  │  └──────────┼──────────┘  │  │
    │  │             │             │  │
    │  │        MAJOR CALYX        │  │
    │  │             │             │  │
    │  └─────────────┼─────────────┘  │
    │                │                │
    │          RENAL PELVIS           │
    │                │                │
    │         PELVI-URETERIC          │
    │           JUNCTION (PUJ)        │
    └─────────────────────────────────┘

• Fibrous capsule
• Cortex (containing glomeruli and convoluted tubules) - 1-1.5 cm thick
• Columns of Bertin (cortex dipping between pyramids)
• Medullary pyramids (contain loops of Henle and collecting ducts)
• Minor calyces (8-18 per kidney) cup the papillae
• Major calyces (2-3) drain into renal pelvis
• Renal pelvis narrows to form ureter at PUJ
• Renal sinus (contains fat, vessels, lymphatics)

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Classification of Congenital Anomalies of Urinary System

A. Anomalies of Number

1. Renal agenesis (bilateral - Potter sequence; unilateral - compensatory hypertrophy)
2. Supernumerary kidney

B. Anomalies of Position (Ectopia)

1. Simple renal ectopia (pelvic, iliac, abdominal)
2. Crossed renal ectopia (with or without fusion)
3. Intrathoracic kidney

C. Anomalies of Form/Fusion

1. Horseshoe kidney
2. Crossed fused ectopia
3. Lump/discoid/cake kidney

D. Anomalies of Rotation

1. Malrotation (incomplete or reverse rotation)

E. Anomalies of Size

1. Renal hypoplasia (small but normally functioning kidney)
2. Renal aplasia

F. Cystic Anomalies

1. Autosomal dominant polycystic kidney disease (ADPKD)
2. Autosomal recessive polycystic kidney disease (ARPKD)
3. Medullary sponge kidney
4. Multicystic dysplastic kidney (MCDK)
5. Simple renal cysts
6. Nephronophthisis

G. Anomalies of Renal Pelvis and Ureter

1. Pelviureteric junction (PUJ) obstruction
2. Duplex kidney/bifid ureter
3. Retrocaval ureter
4. Ureterocele
5. Vesicoureteral reflux (VUR)
6. Megaureter

H. Anomalies of Bladder/Urethra

1. Bladder exstrophy
2. Urachal anomalies
3. Posterior urethral valves (PUV)

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Three Renal Anomalies in Detail

1. Horseshoe Kidney

• Failure of normal cranial ascent and lateral rotation during embryological development
• The isthmus hooks behind the inferior mesenteric artery (IMA), preventing normal ascent
• Kidneys lie lower than normal (L3-L5 level instead of T12-L2)

• Absence of normal renal outline
• Kidneys appear lower

• Lower poles of both kidneys connected by a band of tissue anterior to the great vessels
• Abnormal axis (lower poles medially directed)
• Associated hydronephrosis in ~30%

• Classic "U-shaped" or "horseshoe" configuration
• Isthmus anterior to aorta
• Malrotation with anteriorly facing pelvis and laterally pointing calyces
• Aberrant vasculature (multiple vessels from aorta, common iliac, superior mesenteric arteries)

• Medially directed lower pole calyces
• "Flower vase" appearance of collecting systems
• Axis of kidneys reversed (lower poles medial)

• PUJ obstruction and hydronephrosis (most common complication)
• Recurrent UTI
• Calculi (20-60%)
• Increased risk of trauma (due to anterior position)
• Associated Wilms tumor risk (horseshoe kidney is risk factor)
• Transitional cell carcinoma (slightly increased risk)
• Associated anomalies: Turner syndrome, trisomy 18, cardiac defects

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2. Autosomal Dominant Polycystic Kidney Disease (ADPKD)

• Abnormal polycystin-1 or polycystin-2 proteins (components of tubular cilia)
• Progressive cyst formation from all nephron segments
• Cysts expand, compressing normal parenchyma
• End-stage renal disease in 50% by age 60

• Bilaterally enlarged renal shadows
• May show calcified cyst walls

• Bilaterally massively enlarged kidneys
• Innumerable cysts of varying sizes
• Loss of corticomedullary differentiation
• Cysts may contain internal echoes (hemorrhage, infection)
• Extrarenal cysts in liver (most common extrarenal site), pancreas, spleen, seminal vesicles
• Unified Pei-Ravine criteria for USG diagnosis:
  • Age 15-39: ≥3 cysts (unilateral or bilateral)
  • Age 40-59: ≥2 cysts in each kidney
  • Age ≥60: ≥4 cysts in each kidney

• Bilaterally enlarged kidneys (can weigh >1 kg each)
• Hundreds of cysts of varying densities
• Hyperdense cysts on NCCT = hemorrhagic cysts
• Enhancement of cyst walls indicates infection/malignant transformation
• Total kidney volume (TKV) measured by CT - best predictor of disease progression
• Hepatic cysts in 80%
• Extrarenal manifestations: intracranial aneurysms (10-15%)

• T2WI: Multiple bilateral hyperintense cysts
• T1WI: Hemorrhagic cysts hyperintense on T1
• More sensitive than CT for small cysts
• Better for volumetric assessment without radiation

• Hypertension (75% of patients)
• Renal failure (ESRD)
• Cyst hemorrhage (30-50%)
• Cyst infection
• Renal calculi (20%)
• Intracranial berry aneurysm (rupture causing SAH)
• Mitral valve prolapse
• Diverticular disease of colon

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3. Pelviureteric Junction (PUJ) Obstruction

• Intrinsic: Abnormal smooth muscle, aperistaltic segment, mucosal folds, high insertion of ureter
• Extrinsic: Crossing lower polar vessel (most common extrinsic cause in adults), adhesions, bands

• Hydronephrosis (dilated pelvis ≥10 mm at 28 weeks)
• Normal ureter (distinguishes from vesicoureteral junction obstruction)
• Normal bladder

• Dilated renal pelvis (anteroposterior diameter >10 mm)
• Dilated calyces (caliectasis)
• Normal or non-visualized ureter
• Cortical thinning in severe cases
• Power Doppler: may show crossing vessel

• Obstructed drainage curve (F+20 pattern)
• t½ of tracer washout >20 minutes = obstruction
• Differential renal function: affected kidney may show reduced function
• Lasix (furosemide) augmented study to differentiate obstruction from dilated non-obstructed system

• Sudden transition from dilated renal pelvis to normal ureter at PUJ
• Perinephric stranding in acute obstruction
• May demonstrate crossing vessel
• Volume of renal pelvis

• Dense nephrogram with delayed opacification
• Dilated pelvicalyceal system
• Abrupt termination at PUJ
• "Rim sign" or "crescent sign" in severe obstruction

• Gold standard anatomical assessment
• Shows exact level and nature of obstruction

• Post-pyeloplasty: Follow-up MAG3 scan to assess improvement
• Serial USG for moderate hydronephrosis managed conservatively

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3. USG and CT Findings in Five Adrenal Lesions

1. Adrenal Adenoma

• Small (usually <3 cm), well-defined, homogeneous, hypoechoic mass
• Round/oval shape, smooth margins
• Difficult to detect on USG if <2 cm

• Non-contrast: Homogeneous, smooth margins, density <10 HU (lipid-rich) - most specific finding
• Contrast: Rapid washout on delayed phase
• Absolute washout >60% or relative washout >40% at 15 min = adenoma
• Lipid-poor adenoma: density 10-30 HU, still shows rapid washout
• No necrosis, no calcification, no adjacent invasion

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2. Pheochromocytoma

• Variable echogenicity - may be hyperechoic or complex
• Large mass (average 5-6 cm at presentation)
• May show cystic areas (necrosis)
• Difficult to characterize

• Large, heterogeneous mass
• May show cystic/necrotic areas, calcification
• Intense enhancement (hypervascular) on contrast
• Salt-and-pepper appearance
• High density on NCCT (>35 HU) unlike adenoma
• 10% rule - 10% bilateral, 10% extraadrenal (paraganglioma), 10% malignant, 10% in children
• Extra-adrenal locations along sympathetic chain (organ of Zuckerkandl)
• Diagnosis confirmed by 24-hour urinary catecholamines/metanephrines

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3. Adrenal Cortical Carcinoma (ACC)

• Large heterogeneous mass (usually >6 cm)
• Mixed echogenicity with cystic/necrotic areas
• May show calcification (shadowing)
• IVC involvement - intraluminal tumor thrombus

• Large (>6 cm) heterogeneous mass
• Irregular margins, capsular invasion
• Central necrosis, hemorrhage, calcification
• Poor or heterogeneous enhancement
• Venous invasion (IVC, adrenal vein) - tumor thrombus
• Liver metastases, lymphadenopathy
• Contralateral adrenal metastases
• Staging uses CT chest/abdomen/pelvis

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4. Adrenal Myelolipoma

• Hyperechoic mass (due to fat and myeloid tissue)
• Well-defined, smooth margins
• May show posterior acoustic enhancement
• No internal vascularity on Doppler

• Diagnostic finding: Macroscopic fat (density -30 to -100 HU) within the mass
• Mixed density - fat (-100 HU) + soft tissue (myeloid elements)
• Well-defined, no enhancement in fatty areas
• May show calcification
• No adrenal insufficiency, no hormonal activity
• Rarely can be bilateral

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5. Adrenal Metastases

• Bilateral (most common bilateral adrenal lesion after adenoma)
• Hypoechoic to isoechoic, heterogeneous
• Irregular margins in large lesions
• Variable echogenicity

• Round/irregular bilateral masses (bilateral in 50%)
• Density >30 HU on NCCT
• No lipid content (unlike adenoma)
• Heterogeneous enhancement, slow washout
• Absolute washout <60% at 15 min
• Necrotic areas in large lesions
• Rim enhancement possible
• Primary tumors: lung, breast, melanoma, colon, kidney, lymphoma
• Adrenal enlargement with maintained shape initially

• FDG-avid metastases
• Allows characterization of equivocal lesions

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4. Renal Cell Carcinoma (RCC)

Definition

Histological Types

• Clear cell (conventional) RCC - 75-80%, most common, arises from proximal tubule
• Papillary RCC - 10-15%, two subtypes
• Chromophobe RCC - 5%, better prognosis
• Collecting duct carcinoma - rare, poor prognosis
• Unclassified - 3-5%

Triad (Classic - seen in only 10%)

1. Flank pain
2. Palpable mass
3. Hematuria (gross or microscopic)

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Radiology

Plain X-ray (KUB)

• Enlarged renal shadow
• Calcification (10%) - irregular, "eggshell" type
• Bone metastases (lytic, expansile)

USG

• Variable echogenicity - may be hyperechoic, hypoechoic, or isoechoic
• Hyperechoic small RCC may mimic angiomyolipoma (but no acoustic shadowing, less bright)
• Complex cystic lesion (Bosniak III/IV)
• May show intratumoral vascularity on Doppler
• Tumor thrombus in renal vein/IVC
• Regional lymphadenopathy

CT (Gold Standard for Staging)

• Exophytic or intrarenal mass
• Heterogeneous density
• Calcification (10%)

• Enhancement >20 HU = malignancy
• Clear cell RCC: Avidly enhancing (hypervascular), heterogeneous due to necrosis/hemorrhage
• Papillary RCC: Minimally enhancing (hypovascular), homogeneous
• Chromophobe RCC: Moderate enhancement

• Collecting system invasion
• Pseudocapsule

• Beak sign - parenchymal rim around the tumor
• Tumor thrombus in renal vein extending to IVC (seen in 10-25%)
• "Claw sign" - normal kidney wrapping around mass
• Perinephric fat invasion (stage T3a)
• Contralateral kidney - must be assessed

CT Staging (TNM)

MRI

• Better than CT for:
  • IVC thrombus extent (T3b/T3c)
  • Distinguishing tumor thrombus from bland thrombus
  • Equivocal CT cases
  • Avoiding radiation/contrast

• T1WI: Intermediate to low signal; hemorrhagic areas hyperintense
• T2WI: Heterogeneous, slightly hyperintense to renal cortex
• T1 with gadolinium: Avid enhancement in clear cell type
• Pseudocapsule: hypointense rim on T2WI
• DWI: Restricted diffusion

• Preoperative mapping of renal artery anatomy
• Venous involvement

PET-CT

• Limited role (RCC is not FDG-avid reliably)
• Useful for detecting metabolically active metastases
• Carbonic anhydrase IX (CAIX) targeted PET agents used in research

Bone Scan

• For bone metastases
• RCC gives lytic, expansile metastases ("blowout" metastases)
• Hypervascular metastases - also seen on angiography

Angiography

• Preoperative embolization for large tumors
• Hypervascular tumor "tumor blush"
• Arteriovenous malformations within tumor

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Differential Diagnosis on Imaging

• Angiomyolipoma (fat density on CT distinguishes it)
• Oncocytoma (central scar, spoke-wheel pattern - cannot reliably distinguish from RCC)
• Lymphoma (multiple bilateral masses, retroperitoneal disease)
• Metastases to kidney

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5. Testicular Torsion

Definition

Types

• Intravaginal torsion - commonest (within the tunica vaginalis); associated with "bell-clapper deformity"
• Extravaginal torsion - neonatal, entire processus vaginalis rotates
• Torsion of appendix testis (hydatid of Morgagni) - most common cause of acute scrotum in boys 7-12 years

Clinical Features

• Sudden onset severe unilateral scrotal pain
• Nausea, vomiting
• Absent cremasteric reflex (most reliable clinical sign)
• Peak age: 12-18 years (second peak in neonates)

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Radiology - High-Frequency USG with Doppler (Investigation of Choice)

Grayscale Findings:

• Testis may appear normal in size and echogenicity
• Reactive hydrocele
• Scrotal wall edema

• Testis enlargement
• Heterogeneous (hypoechoic) echotexture
• Epididymal enlargement and heterogeneity
• Reactive hydrocele

• Marked heterogeneity and hypoechogenicity
• Loss of normal testicular architecture
• Scrotal wall thickening

Doppler Findings (KEY):

• Absent or markedly reduced intratesticular blood flow on the affected side
  • Compare with contralateral side (must be done)
  • Color Doppler shows no flow or minimal flow
• In incomplete torsion: reduced (not absent) flow
• Epididymal hyperemia (epididymo-orchitis shows increased epididymal flow)

• Pathognomonic for torsion
• Twisting of the spermatic cord seen on Color Doppler (spiral/coiled appearance of cord)
• Best seen at the external inguinal ring

• After detorsion - increased flow (reactive)

Sensitivity and Specificity:

• Color Doppler USG: Sensitivity 88-100%, Specificity 90-100%
• Note: In neonates, normal flow may be absent even without torsion - use caution

MRI (rarely used, when USG equivocal):

• T1WI: Torted cord - spiral/twisted appearance
• T2WI: Heterogeneous low signal (infarction)
• No gadolinium enhancement = absent perfusion

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Imaging Pitfalls

• Spontaneous detorsion may show increased flow (mimics epididymo-orchitis)
• High-riding testis and horizontal orientation - clinical clues
• Do not delay surgery for imaging if clinical suspicion is high

Management Decision

• USG confirmation → immediate surgical exploration
• "Time is testicle" - salvage rates:
  • <6 hours: 90-100%
  • 6-24 hours: 50-70%

  • 24 hours: <10%

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6. Wilms Tumor (Nephroblastoma)

Definition

Associated Conditions (WAGR Syndrome)

• Wilms tumor
• Aniridia
• Genitourinary malformations
• Retardation (mental)

Pathology

• Triphasic: blastema, epithelium, stroma
• Favorable histology (>90%) vs unfavorable (anaplastic type)

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Radiology

Plain X-ray Abdomen

• Soft tissue abdominal mass, displaces bowel
• May show calcification (rarely, unlike neuroblastoma)
• "Mass effect" on bowel

USG (First investigation)

• Large intrarenal solid mass, well-defined pseudocapsule
• Heterogeneous echogenicity (mixed solid and cystic)
• Cystic areas: necrosis, hemorrhage
• Involvement of renal parenchyma (intrarenal origin - helps distinguish from neuroblastoma)
• IVC and renal vein tumor thrombus (10-15%) - evaluated on Doppler
• Contralateral kidney - assess for bilateral disease
• Liver metastases
• Lymph node assessment

CT (Gold Standard for Staging)

• Large heterogeneous intrarenal mass
• Hypodense areas (necrosis, cystic degeneration)
• Calcification (10-15%, less than neuroblastoma)
• "Rim of normal cortex" may be visible (claw sign)

• Heterogeneous enhancement
• Non-enhancing central necrosis
• Pseudocapsule
• Residual normal kidney "claw" embracing tumor
• Collecting system distortion/displacement

MRI

• T1WI: Heterogeneous, intermediate signal
• T2WI: Heterogeneous high signal
• Post-Gd: Heterogeneous enhancement
• Better for IVC/renal vein thrombus extent
• Avoids radiation (important in children)
• Diffusion-weighted imaging: restricted diffusion in solid components

IVU (Largely replaced by CT)

• Intrarenal mass distorting/displacing collecting system
• "Spider-leg" deformity - calyces splayed around the mass
• Functioning remnant kidney around the mass

Chest CT

• Pulmonary metastases (most common distant site)
• Round, well-defined nodules

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7. USG Findings in Three Common Scrotal Pathologies

1. Epididymo-Orchitis

• Enlarged, hyperemic epididymis (head most commonly affected first)
• Epididymis: hypoechoic and enlarged
• Testis: enlarged, hypoechoic (when orchitis develops)
• Reactive hydrocele (anechoic fluid around testis)
• Scrotal wall thickening and edema
• Pyocele - complex echogenic fluid collection (pus)
• Scrotal abscess - irregular walled collection, internal echoes

• Markedly increased vascularity in epididymis and testis ("hyperemia")
• Reversed arterial diastolic flow in severe cases (due to increased pressure)
• Epididymal hypervascularity is cardinal sign

• Abscess formation - complex collection, no internal vascularity
• Testicular infarction - wedge-shaped avascular area
• Fournier's gangrene - gas in scrotal tissues (hyperechoic foci with "dirty" posterior shadowing)

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2. Varicocele

• Multiple tortuous, anechoic tubular structures in the peritesticular region (posterior/superior to testis)
• Diameter >2 mm = varicocele (grade depends on size and reflux)
• Valsalva maneuver increases size (patient asked to bear down during scan)

• Color Doppler: Spontaneous or augmented flow in the dilated veins
• Reflux on Valsalva = diagnostic (reversal of flow direction)
• Intermittent or continuous flow

• Grade I: Palpable only on Valsalva
• Grade II: Palpable at rest
• Grade III: Visible at rest ("bag of worms")

• Must exclude retroperitoneal mass compressing renal vein or IVC
• Nutcracker syndrome (left renal vein compressed between aorta and SMA)

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3. Hydrocele

• Anechoic (echo-free) fluid surrounding the testis and epididymis anterolaterally
• Testis visible within the fluid - normal echotexture and size
• No vascularity within the fluid

• Simple hydrocele - completely anechoic, no septations, no debris
• Complex hydrocele - contains internal echoes (infection = pyocele; hemorrhage = hematocele; cholesterol crystals = chronic)
• Pyocele - echogenic fluid with internal echoes, may have septations
• Hematocele - echogenic/complex fluid collection (blood products)

• Reactivehydrocele in epididymo-orchitis or torsion - small fluid collection
• Hernia - bowel loops within apparent "hydrocele" (peristalsis visible)
• Secondary hydrocele - associated ipsilateral testicular/epididymal pathology

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8. Role of Radiology in Evaluation of Hematuria in Old Age Patient

Significance

Causes in Elderly

1. Bladder transitional cell carcinoma (TCC) - most common serious cause
2. Benign prostatic hyperplasia (BPH) - most common benign cause
3. Prostate carcinoma
4. Renal cell carcinoma
5. Upper tract TCC (renal pelvis/ureter)
6. Renal calculi
7. Anticoagulation therapy
8. Radiation cystitis (post-pelvic radiotherapy)
9. Bladder calculi
10. Chronic kidney disease / interstitial nephritis

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Investigation Protocol

Step 1 - Ultrasound Abdomen and Pelvis

• Bladder (scan with full bladder):
  • Echogenic sessile or papillary mass - TCC
  • Wall thickening and irregularity
  • Associated hydronephrosis (ureteral involvement)
  • Post-void residual urine (BPH)
• Kidneys:
  • Cortical masses (RCC)
  • Hydronephrosis
  • Calculi
  • Cortical scarring
• Prostate (transabdominal):
  • Size estimation
  • Heterogeneity suggesting carcinoma
  • Intravesical protrusion of BPH ("median lobe")
  • Transrectal USG (TRUS) better for prostate assessment

Step 2 - CT Urography (CTU) - PRIMARY INVESTIGATION

• Calculi, calcification
• Baseline densitometry

• Hypervascular masses (RCC)

• Parenchymal lesions
• Renal and perirenal structures

• Bladder filling defects (TCC) - most important for older patients
• Ureteral filling defects
• Bladder wall thickening

• Bladder TCC - polypoid/sessile mass, irregular mural thickening, enhancement; assess depth of invasion (T staging)
• Prostate carcinoma invading bladder - irregular posterior bladder wall, obliteration of fat plane
• Upper tract TCC - filling defects in renal pelvis/ureter
• RCC - enhancing renal mass

Step 3 - CT/MRI Staging

• T1: Confined to mucosa/submucosa
• T2: Muscle invasion (poor prognosis)
• T3: Perivesical fat invasion
• T4: Adjacent organ invasion

• T2WI: Low signal tumor vs high signal normal bladder wall
• Dynamic contrast enhanced (DCE): Early enhancement of tumor
• DWI: Restricted diffusion in tumor
• Superior to CT for detecting muscle invasion

Step 4 - Prostate Assessment

• TRUS (transrectal USG): Hypoechoic peripheral zone lesion
• MRI prostate (mpMRI): T2WI + DWI + DCE - PI-RADS scoring system
• PSA-guided decision making

Step 5 - Flexible Cystoscopy

• Complementary to radiology (not radiological but important in algorithm)
• Direct visualization and biopsy

Step 6 - Nuclear Medicine

• Bone scan: Prostate/bladder cancer metastases
• FDG-PET CT: Lymph node staging, metastatic disease

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9. Hypertrophic Pyloric Stenosis (HPS)

Definition

Epidemiology

• Onset typically 3-6 weeks of age (rarely at birth or >3 months)
• M:F = 4-5:1 (males, especially firstborn)
• Incidence: 1-3 per 1000 live births

Clinical Features

• Non-bilious projectile vomiting (postprandial)
• "Hungry after vomiting" - infant feeds again immediately
• Olive-shaped pyloric mass palpable in right epigastrium
• Metabolic: Hypochloremic, hypokalemic metabolic alkalosis

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Radiology

USG - Investigation of Choice (replaced barium study)

• High-frequency linear probe (7.5-10 MHz)
• Infant fed before scan (to allow visualization of fluid-filled stomach)
• Scan right upper quadrant

• Pyloric muscle thickness (MT) ≥4 mm (most reliable single criterion)
• Pyloric channel length ≥17 mm (some use 16 mm)
• Pyloric transverse diameter >14 mm (outer-outer)
• Target sign / "doughnut sign" on transverse view:
  • Outer echogenic ring (serosa)
  • Hypoechoic ring (thickened circular muscle)
  • Central echogenic dot (mucosa/channel)

• Antral nipple sign - redundant pyloric mucosa prolapsing into the antrum
• No passage of gastric contents through pylorus
• Active gastric peristalsis with failure of pyloric opening
• Stomach dilated, fluid-filled

• Failure of pyloric canal to open over 5-minute observation
• Fluid/food passes from antrum but not through pylorus

Barium Meal (now rarely performed)

• "String sign" (Ravich sign) - thin trickle of barium through the elongated, narrow pyloric channel
• "Double-track sign" or "railroad track sign" - two parallel tracks of barium in the pyloric canal (mucosal folds)
• "Shoulder sign" - indentation on the gastric antrum by the hypertrophied muscle
• "Mushroom sign" - barium base of pyloric canal
• "Caterpillar sign" - prominent gastric peristalsis
• Delayed gastric emptying
• Dilated stomach

Plain X-ray Abdomen

• Dilated stomach with paucity of bowel gas in remaining abdomen
• "Single bubble" - air-distended stomach (not diagnostic)

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Management

• Surgical Ramstedt pyloromyotomy (after correcting electrolytes)
• Post-operative USG/fluoroscopy if symptoms persist

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10. Ureterocele

Definition

Types

1. Simple (orthotopic) ureterocele - single system, ureter enters bladder normally at trigone; common in adults
2. Ectopic ureterocele - ureter opens at abnormal location (bladder neck, urethra); almost always associated with duplex kidney (upper moiety ureter); common in girls, causes incontinence if orifice below external sphincter

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Radiology

USG (Initial Investigation)

• Classic sign: Round/oval thin-walled cystic structure within the bladder lumen (at the uretero-vesical junction)
• "Cobra-head sign" on real-time observation (swelling of ureter as it enters bladder)
• May be seen expanding and contracting with peristalsis
• Associated ipsilateral hydronephrosis (obstructive)
• Duplex kidney assessment (upper moiety hydronephrosis with ectopic ureterocele)
• Bladder calculus within the ureterocele (complication)

• Large ureterocele prolapsing through bladder neck/urethra in girls
• Seen as echogenic mass at introitus on perineal USG

Intravenous Urography (IVU) / CT Urography

• "Cobra-head sign" (or "spring-onion sign") - the ureterocele appears as a smoothly outlined filling defect in the bladder, surrounded by a halo of contrast (edematous ureteral wall)
• Obstructed ipsilateral collecting system (delayed/poor function)
• In ectopic ureterocele with duplex kidney:
  • Non-functioning dilated upper moiety ("drooping lily" sign - lower moiety displaced inferolaterally)
  • "Absent upper calyx" on IVU - upper moiety poorly functioning

• Best modality for complex cases
• Thin-walled cystic structure in the bladder at UV junction
• Obstructed proximal ureter and collecting system
• Duplex anatomy
• Calculus within ureterocele

Voiding Cystourethrography (VCUG)

• Assesses vesicoureteral reflux (into lower moiety in duplex systems)
• Shows filling defect in bladder
• Bladder outlet obstruction in boys with ectopic ureterocele
• Important for surgical planning

MR Urography

• Better delineation of duplex anatomy
• No radiation (important in children)
• Assessment of function via dynamic MR urography

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11. Embryology of Kidney + Congenital Anomalies + Pediatric Renal Solid Lesions

Embryology of Kidney

• Rudimentary, non-functional
• Regresses completely

• Temporary functional kidney
• Mesonephric (Wolffian) duct drains it
• Partially regresses; Wolffian duct persists to form male genital tract

• Formed by interaction of two components:
  • Ureteric bud (outgrowth of Wolffian duct) → ureter, renal pelvis, calyces, collecting ducts
  • Metanephric mesenchyme (blastema) → nephrons (glomeruli to DCT)
• Inductive interaction between ureteric bud and blastema is essential
• Kidney initially in pelvis, ascends to lumbar position (T12-L2) by week 8-9
• During ascent: rotates 90° so pelvis faces medially

• GDNF (from metanephric mesenchyme) stimulates ureteric bud branching
• WT1 gene - essential for metanephric mesenchyme induction

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Congenital Anomalies of Kidney (Classified)

• ARPKD: Bilateral renal enlargement, microcysts (too small for USG), "bright kidneys" on USG; associated with congenital hepatic fibrosis
• MCDK: Unilateral, multiple non-communicating cysts replacing entire kidney; no functioning renal tissue; normal contralateral kidney (compensatory hypertrophy)

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Pediatric Renal Solid Occupying Lesions - Classification and Radioimaging

Classification

1. Mesoblastic nephroma (most common neonatal renal tumor)
2. Multilocular cystic nephroma (MLCN)
3. Angiomyolipoma (AML)
4. Oncocytoma (rare in children)

1. Wilms tumor (nephroblastoma) - most common malignant renal tumor of childhood
2. Clear cell sarcoma of the kidney (CCSK) - "bone metastasizing renal tumor"
3. Rhabdoid tumor of kidney (RTK) - most aggressive; associated with brain tumors
4. Renal medullary carcinoma (sickle cell trait)
5. Translocation RCC (MITF/TFE3) - adolescents
6. Lymphoma

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Radioimaging Features

• Large intrarenal mass, pseudocapsule, heterogeneous
• Rarely calcified, IVC thrombus common
• Contrast CT: characteristic features

• Most common renal tumor in neonates (<3 months)
• USG: Large, predominantly solid intrarenal mass, hypoechoic
• CT: Solid, homogeneous, centered in renal sinus, concentric ring pattern ("ring sign")
• "Polyhydramnios" detected antenatally on fetal USG
• Good prognosis (classic type) vs intermediate prognosis (cellular type)

• Also called "bone metastasizing renal tumor of childhood"
• USG/CT: Resembles Wilms tumor; intrarenal mass, heterogeneous
• Distinguishing feature: Bone metastases at diagnosis (unlike Wilms)
• Cystic change more prominent
• Bone scan essential for staging

• Most aggressive; often metastatic at presentation
• USG/CT: Lobulated subcapsular fluid collections (due to tumor dissecting under capsule)
• Subcapsular hematoma
• Intratumoral calcification common (curvilinear)
• Brain tumors (PNET/medulloblastoma) in 15%
• Poor prognosis

• Well-defined multiloculated cystic mass
• Herniates into renal pelvis (characteristic)
• CT: Multiple non-communicating cysts, no solid enhancement
• MRI: T2 hyperintense locules
• Bimodal age distribution: boys <4 years and women 40-60 years

• Bilateral multiple hypoechoic nodules
• CT: bilateral masses, retroperitoneal lymphadenopathy
• No calcification or IVC thrombus

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12. Imaging and Color Doppler Findings in Acute Scrotum

Definition

Causes

1. Testicular torsion (emergency - 6 hours window)
2. Torsion of appendix testis
3. Epididymo-orchitis
4. Strangulated hernia
5. Trauma (hematocele)
6. Fournier's gangrene
7. Idiopathic scrotal edema

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High-Frequency Color Doppler USG (Investigation of Choice)

• 10-15 MHz linear array transducer
• Both sides scanned and compared
• Grayscale + Color Doppler + Power Doppler + Spectral analysis
• Valsalva maneuver for varicocele assessment

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Imaging Findings by Cause

1. Testicular Torsion (covered in Question 5)

• Complete absence of intratesticular blood flow on affected side
• Contralateral testis shows normal flow (comparison mandatory)
• Whirlpool sign - coiled spermatic cord
• Grayscale: heterogeneous testis, reactive hydrocele, scrotal wall edema

2. Torsion of Appendix Testis

• Most common cause of acute scrotum in boys 7-12 years
• Grayscale USG: Small, round hyperechoic or hypoechoic nodule adjacent to the upper pole of testis/epididymis
• "Blue dot sign" clinically (visible through scrotal skin)
• Reactive hydrocele
• Doppler: Normal testicular flow (distinguishes from testicular torsion), hyperemia of surrounding structures
• Enlarged, hyperemic epididymis head

3. Epididymo-Orchitis (covered in Question 7)

• Markedly increased flow in epididymis and testis
• Epididymal enlargement with hypervascularity is hallmark
• Contralateral comparison confirms asymmetric hyperemia
• Spectral Doppler: Low-resistance waveform (increased diastolic flow)

4. Strangulated/Incarcerated Hernia

• Grayscale: Echogenic or heterogeneous mass in scrotal neck/inguinal canal
• Bowel loops with peristalsis visible (in hernia content)
• Absent peristalsis = strangulation
• Echogenic fat = omental hernia
• Doppler: Absent or reduced mural flow in strangulated bowel
• Reactive hydrocele, scrotal wall edema

5. Hematocele (Trauma)

• Grayscale: Complex echogenic fluid collection surrounding the testis
• Acute blood = echogenic; old blood = more anechoic
• Testicular rupture: disrupted tunica albuginea (heterogeneous parenchyma, irregular margin)
• Doppler: Absent flow in ruptured/infarcted segments
• Fracture line: heterogeneous avascular band through testis

6. Fournier's Gangrene

• Necrotizing fasciitis of perineum/scrotum - life-threatening emergency
• Grayscale: Thickened scrotal wall with echogenic foci (gas) casting dirty posterior acoustic shadowing
• "Dirty shadowing" from subcutaneous gas = pathognomonic
• CT is preferred for full extent assessment
• CT: Gas in scrotal fascial planes, perineal tissues

7. Segmental Testicular Infarction

• Wedge-shaped peripheral hypoechoic area
• Absent flow on Doppler in infarcted segment
• Remaining testis has normal flow
• May simulate tumor clinically and on USG
• MRI may help - avascular wedge on DCE

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Comparison Table - Acute Scrotum USG

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13. MRI Findings for Adnexal Lesions

Categories of Adnexal Lesions

A. Ovarian Lesions

• T1WI: Hypointense
• T2WI: Markedly hyperintense (pure fluid)
• T1+Gd: No enhancement
• Thin imperceptible wall
• Follow-up based on size (>5 cm in premenopausal, any in postmenopausal needs work-up)

• T1WI: Hyperintense (blood products) - key finding
• T2WI: Variable (may show "T2-dark" or heterogeneous)
• T1 fat sat: Remains bright (blood, not fat)
• No enhancement
• "Fishnet" or "lacy" internal pattern on T2 (fibrin strands)
• No solid component - no enhancement

• T1WI: High signal (hyperintense) - due to methemoglobin in chronic blood
• T1 fat-saturated: Remains bright (distinguishes from fat - dermoid)
• T2WI: "T2 shading" - loss of signal intensity (chronic blood products)
• T2WI: Hypointense rim (hemosiderin deposition)
• Multiple lesions, bilateral common
• "Kissing ovaries" - bilateral endometriomas adherent in cul-de-sac

• T1WI: Hyperintense (fat content) - key finding
• T1 fat-saturation: Signal drops (fat suppression) - confirms fat
• T2WI: Heterogeneous
• Chemical shift artifact at fat-fluid interface
• Rokitansky nodule (dermoid plug): focal mural solid nodule, contains teeth/bone (dark on all sequences)
• "Floating fat-fluid level" on MRI
• Low DWI signal (fat)

• Serous cystadenoma: Unilocular thin-walled cyst, T2 bright, no enhancement
• Serous cystadenocarcinoma: Complex cystic-solid mass, papillary projections, septal enhancement
• T2WI: High signal cystic components
• T1+Gd: Enhancement of solid components, septa, papillary projections
• DWI: Restricted diffusion in malignant solid areas
• Peritoneal implants, ascites in advanced disease

• Multiloculated cystic mass
• "Stained glass" appearance - locules of varying T1/T2 signal (different mucin concentrations)
• T1WI: Some locules hyperintense (mucinous content)
• T2WI: Hyperintense (but less bright than simple cyst)
• T1+Gd: Thin enhancing septations (benign); thick enhancing walls/septa + solid areas (malignant)
• Large size, extending to entire pelvis

• T1WI: Low-intermediate signal
• T2WI: Markedly hypointense (fibrous tissue - key feature)
• T1+Gd: Minimal enhancement (fibrous, hypovascular)
• Associated with Meigs syndrome (fibroma + ascites + pleural effusion)
• Associated with Gorlin syndrome (basal cell nevus syndrome)

• Complex solid-cystic pelvic mass
• DWI: Restricted diffusion in solid components (low ADC)
• T1+Gd: Enhancement of solid elements
• Peritoneal carcinomatosis: T2 high signal nodules on peritoneal surfaces
• Omental cake: T2 heterogeneous omental mass
• Lymphadenopathy (paraaortic, iliac)

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B. Fallopian Tube Lesions

• Dilated, tortuous tubular structure
• T2WI: Folded, C or S-shaped hyperintense tubular structure
• No solid component
• Incomplete septa (key feature - distinguishes from multilocular cyst)
• No enhancement of wall

• Complex adnexal mass with internal debris
• T1WI: Variable (hemorrhage or proteinaceous content may be T1 bright)
• T2WI: Hyperintense fluid, thick enhancing walls
• T1+Gd: Rim enhancement of abscess wall
• DWI: Restricted diffusion within pus (ADC low)
• Loss of normal fat plane with adjacent structures
• Associated free fluid, pelvic peritonitis

• Ring-of-fire sign on Doppler USG (vascular trophoblastic ring)
• On MRI: Gestational sac-like structure in tube
• T1+Gd: Ring enhancement
• Hemoperitoneum: T1 bright blood

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C. Parametrial/Peritoneal Lesions

• Post-surgical/inflammatory; fluid trapped by adhesions around ovary
• Conforms to peritoneal space shape
• T2WI: Complex cyst around ovary (ovary seen as "spider in a web")
• No enhancement of internal structure
• Normal ovary identifiable within

• T2WI: Hypointense (similar to uterine fibroid)
• Separate from ovary
• T1+Gd: Variable enhancement
• Shows "bridging vascular sign" to uterus on MRI

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O-RADS MRI Score

• O-RADS 1: No lesion
• O-RADS 2: Almost certainly benign (simple cyst)
• O-RADS 3: Low risk (<10% malignancy)
• O-RADS 4: Intermediate risk (10-50%)
• O-RADS 5: High risk (>50% malignancy)

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14. Cut Section of Kidney + Role of USG in Painless Hematuria

Cut Section of Kidney

• Renal capsule → Cortex (1.0-1.5 cm) → Medullary pyramids → Papillae → Minor calyces → Major calyces → Renal pelvis → PUJ → Ureter

• Kidney length: 9-12 cm (right slightly smaller)
• Cortical thickness: ≥1 cm (normal), <0.7 cm (thinned)
• Echogenicity: Cortex < liver/spleen echogenicity (normal)
• Corticomedullary differentiation: Distinct in normal kidneys

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Role of USG in Painless Hematuria

USG Protocol for Painless Hematuria

1. Size and echogenicity - Enlarged kidneys in polycystic disease; small echogenic kidneys in CKD
2. Masses:
   • Hyperechoic: Angiomyolipoma (fat), small RCC
   • Hypoechoic: Solid tumors, lymphoma
   • Complex cystic: RCC (cystic type), TCC
   • Bosniak classification applied to cystic lesions
3. Pelvicalyceal system:
   • Dilatation = obstruction (TCC obstructing ureter)
   • Filling defects = clot, TCC
4. Calculi: Hyperechoic with posterior acoustic shadowing
5. Renal vein/IVC: Doppler for tumor thrombus

• Not normally seen on USG unless dilated
• Dilated ureter: calculus or TCC causing obstruction
• Doppler: Ureteral jets in bladder (absent = obstruction)

• Scan with full bladder (minimum 300 mL)
• TCC Bladder features:
  • Sessile or papillary echogenic mass
  • Fixed (not mobile like calculus)
  • Irregular mural thickening (>4 mm diffuse, >8 mm focal = suspicious)
  • Vascular on Doppler
  • Posterior wall and trigone most common sites
  • Hydronephrosis if ureteral orifice involved
• Bladder calculus: Echogenic, mobile, posterior shadowing
• BPH: Enlarged prostate, intravesical prostatic protrusion, trabeculated bladder, post-void residual
• Bladder diverticulum: Potential site for TCC

• Enlarged prostate (BPH)
• Asymmetric echogenicity suggesting carcinoma
• Post-void residual volume

• Cannot reliably detect ureteral TCC (ureter not usually visible)
• Small bladder tumors (<1 cm) may be missed
• Cannot assess renal papillae/papillary necrosis reliably
• Radiation injury/cystitis changes difficult to characterize

1. USG first (quick, available, no radiation)
2. If positive finding - CT for staging/characterization
3. If negative on USG but hematuria persists - CT urography mandatory
4. Cystoscopy - always required to exclude small bladder tumors

• "Twinkling artifact" behind calculi (confirms calculus)
• Tumor vascularity
• Ureteral jets (assess ureteral patency)
• IVC thrombus in RCC

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