1. All about Imaging renal tumors radiology

1. All about Imaging renal tumors radiology keep more images, benign malignant both 2. all about Imaging all renal infection and it's complications and genitourinary tb. Make more tables and flow charts

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IMAGING OF RENAL TUMORS & RENAL INFECTIONS - COMPREHENSIVE RADIOLOGY GUIDE

Sources: Grainger & Allison's Diagnostic Radiology (9780323760751), Brenner & Rector's The Kidney (9780323532655), Campbell Walsh Wein Urology (9780323546423)

PART 1: IMAGING OF RENAL TUMORS

Overview: Imaging Modalities for Renal Masses

Modality	Role	Key Advantage
Ultrasound (US)	First-line; cyst vs. solid differentiation	No radiation; widely available
CE-CT (multiphase)	Gold standard for detection, characterisation, staging	>90% accuracy; detects fat, calcification
MRI	Problem-solving; fat detection; VHL surveillance	Superior soft-tissue contrast; no iodinated contrast
CT Urography (CTU)	Upper tract urothelial tumours	Sensitivity 97%, specificity 93% for TCC
PET	Limited role in RCC	Used in metastatic staging/monitoring
Angiography	Spoked-wheel sign in oncocytoma; vascular mapping	Pre-op embolisation

CT Protocol for Renal Mass

┌─────────────────────────────────────────────────────────┐
│            CT RENAL MASS PROTOCOL (4-PHASE)             │
├──────────────┬──────────────────────────────────────────┤
│ UNENHANCED   │ Detect calcification, fat (<-10 HU AML)  │
│              │ Baseline HU measurement                   │
├──────────────┼──────────────────────────────────────────┤
│ CORTICO-     │ ~25-40 sec post-contrast                  │
│ MEDULLARY    │ Detect angiogenesis (clear cell RCC)      │
│ PHASE        │ Identify pseudotumours                    │
├──────────────┼──────────────────────────────────────────┤
│ NEPHRO-      │ ~80-100 sec post-contrast                 │
│ GRAPHIC      │ BEST PHASE for tumour detection           │
│ PHASE        │ Most tumours maximally conspicuous here   │
├──────────────┼──────────────────────────────────────────┤
│ EXCRETORY/   │ ~5-10 min post-contrast                   │
│ PYELOGRAPHIC │ Assess collecting system, TCC             │
│ PHASE        │ Filling defects in renal pelvis/ureter    │
└──────────────┴──────────────────────────────────────────┘

Enhancement criteria:
  ↑ >20 HU (unenhanced → nephrographic) = DEFINITE enhancement → NEOPLASM
  ↑ 10-20 HU = EQUIVOCAL → MRI or biopsy
  ↑ <10 HU = NO enhancement → likely cyst
  Pseudoenhancement: artefact from CT reconstruction algorithms in small cysts

BENIGN RENAL TUMORS

1. Angiomyolipoma (AML)

Pathology: Benign hamartoma - fat + smooth muscle + vascular elements (±cartilage)

Imaging:

AML CT scan - fat-containing mass projecting from left kidney with enhancement in all phases

Fig. Angiomyolipoma: CT noncontrast (A), corticomedullary phase (B), nephrographic phase (C), and excretory phase (D). The fat-containing mass projects anteriorly from the left kidney and demonstrates enhancement throughout. - Brenner & Rector's The Kidney

Feature	Finding
US	Solid, hyperechoic (due to fat)
CT - unenhanced	Low attenuation < -10 HU (macroscopic fat) - DIAGNOSTIC
CT - enhanced	Variable enhancement depending on composition
MRI T1	High signal (fat)
MRI T2	High signal (fat)
MRI - fat saturation	Signal drops on fat-suppressed sequences
Opposed-phase MRI	"India ink" artifact at tumour-parenchyma interface
Minimal-fat AML	Only tiny fat; very difficult - use chemical shift MRI

Key Points:

Fat in any renal lesion = AML virtually certain
Multiple/bilateral AMLs → think Tuberous Sclerosis
AML ≤4 cm: monitor
AML >4 cm: increased haemorrhage risk → consider surgery/embolisation
Wunderlich syndrome = spontaneous retroperitoneal haemorrhage from AML

2. Oncocytoma

Pathology: Benign; arises from proximal collecting tubule epithelium; ~5-7% of renal tumours

Feature	Finding
CT	Solid mass, homogeneous enhancement; central stellate scar (25-30% of cases)
MRI	Homogeneous; central scar hypointense on T1, variable T2
Angiography	Classic "spoked-wheel" pattern
CEUS	Rim enhancement

Key Imaging Challenge: Cannot reliably distinguish from RCC on CT. Surgery generally required for diagnosis.

Recent MRI evidence: combined ADC values (diffusion-weighted) + enhancement ratios on multiphasic MRI may differentiate oncocytoma from malignancy, but not yet validated for routine practice.

3. Renal Adenoma

Most common benign renal tumour
Almost always <2-3 cm
Location: corticomedullary
US: solid appearance
CE-CT: uniform enhancement
No characteristic features to distinguish from other solid tumours

4. Renal Cysts - Bosniak Classification

BOSNIAK CLASSIFICATION SYSTEM
────────────────────────────────────────────────────────────────────
Category │ Features                          │ Malignancy │ Management
─────────┼───────────────────────────────────┼────────────┼──────────
I        │ Simple cyst; thin wall; water      │ ~0%        │ No follow-up
         │ attenuation; no enhancement        │            │
─────────┼───────────────────────────────────┼────────────┼──────────
II       │ Few thin septae (<1 mm)            │ <5%        │ No follow-up
         │ Fine calcifications; <3 cm         │            │
         │ High-density cysts (>70 HU)        │            │
         │ Nonenhancing                       │            │
─────────┼───────────────────────────────────┼────────────┼──────────
IIF      │ Multiple thin septae               │ ~5-10%     │ Imaging
         │ Slightly thickened walls/septae    │            │ follow-up
         │ Coarse/nodular calcification       │            │
         │ Minimal perceived enhancement      │            │
─────────┼───────────────────────────────────┼────────────┼──────────
III      │ Thick irregular walls or septae    │ ~50%       │ Surgical
         │ Measuring enhancement present      │            │ resection
─────────┼───────────────────────────────────┼────────────┼──────────
IV       │ Solid enhancing components         │ ~90-100%   │ Surgical
         │ Enhancing nodules in wall          │            │ resection
────────────────────────────────────────────────────────────────────

Bosniak IV left renal cyst with internal solid component

Fig. Bosniak category IV left renal cyst - CT coronal nephrographic phase. Left lower pole cystic mass with internal solid component - proved to be papillary type RCC. Right lower pole solid mass with central necrosis is clear cell RCC. Right upper pole shows Bosniak I cysts. - Brenner & Rector's

Bosniak IV cyst - Power Doppler confirming vascular nodule; CEUS showing arterial enhancement

Fig. Bosniak category IV cyst, 58F. (A) Grey-scale US: complex cyst with solid nodular component. (B) Power Doppler: flow within nodule confirming vascularisation. (C) CEUS: dense arterial-phase enhancement with heterogeneous washout - clear cell carcinoma Fuhrman grade 2. - Brenner & Rector's

MALIGNANT RENAL TUMORS

1. Renal Cell Carcinoma (RCC)

Epidemiology: Most common renal malignancy (85%); peak 60-70 years; M>F

Histological Subtypes and Imaging Features:

Subtype	Frequency	CT Enhancement	CT Characteristics	MRI
Clear Cell (ccRCC)	70-75%	Avid heterogeneous enhancement	Large; haemorrhage + necrosis common	Heterogeneously hyperintense T2; hypointense T1
Papillary	10-15%	Mild (25-30 HU only)	Often bilateral/multifocal; calcification	Hypointense T2 (haemosiderin); enhancement poor
Chromophobe	5%	Mild (25-30 HU)	Spoke-wheel pattern; calcification	Hypointense T2
Collecting duct	<1%	Variable	Central; infiltrative	Variable

CT Enhancement Rule:

Clear cell: >84 HU corticomedullary phase (avid)
Papillary/Chromophobe: typically <84 HU (mild)

RCC CT scan - right renal mass appears hyperdense on non-contrast; enhanced scans show enhanced structure surrounded by normal kidney

Fig. Renal cell carcinoma CT. (A) Non-contrast: right renal mass slightly hyperdense. (B,C,D) Enhanced: mass enhancement surrounded by normal renal parenchyma - nephrographic and coronal phases demonstrate stage I RCC. - Brenner & Rector's

Robson Staging of RCC:

ROBSON STAGING - RENAL CELL CARCINOMA
══════════════════════════════════════════════════════════
Stage I   │ Confined to renal parenchyma by renal capsule
          │ CT: mass within kidney; intact pseudocapsule
──────────┼───────────────────────────────────────────────
Stage II  │ Extends through capsule into PERINEPHRIC FAT
          │ Still within GEROTA'S FASCIA
          │ CT: stranding in perinephric fat; Gerota intact
──────────┼───────────────────────────────────────────────
Stage III │ IIIA: Tumour extends into RENAL VEIN or IVC
          │ IIIB: Regional retroperitoneal lymph nodes
          │ IIIC: Veins AND nodes
──────────┼───────────────────────────────────────────────
Stage IVA │ Outside Gerota's fascia
          │ Adjacent organ invasion (not ipsilateral adrenal)
──────────┼───────────────────────────────────────────────
Stage IVB │ DISTANT METASTASES
          │ Sites: Lungs > Mediastinum > Liver > Bone
══════════════════════════════════════════════════════════

IVC Thrombus Assessment (Stage IIIA):

CT: filling defect in renal vein/IVC; enhancing thrombus = tumour thrombus
MRI: highly accurate for IVC involvement - coronal gadolinium-enhanced T1WI
Key to surgery: level of IVC thrombus determines approach (infrahepatic vs. suprahepatic)

Metastatic clear cell RCC stage IV - MRI T2 large heterogeneous mass invading liver; coronal gadolinium T1 showing IVC invasion to hepatic vein level

Fig. Metastatic clear cell RCC, stage IV. (A,B) T2-weighted and gadolinium-enhanced T1 axial: large heterogeneous mass, liver invasion and peritoneal metastases. (C,D) Coronal T1+Gad: IVC invasion to level of hepatic veins (arrowheads). - Brenner & Rector's

MRI Features of RCC:

MRI Sequence	Finding
T1WI	Hypointense to isointense (heterogeneous with haemorrhage = hyperintense foci)
T2WI	Most commonly heterogeneously hyperintense
Pseudocapsule	Hypointense rim on T2 (best for staging; if intact → perinephric fat not invaded)
DWI	Restricted diffusion; ADC values aid characterisation
Gad-enhanced	Enhances less than normal cortex; clear cell > papillary > chromophobe
Opposed-phase	Intraluminal lipid causes signal drop

2. Transitional Cell Carcinoma (TCC/Urothelial Carcinoma)

Locations: Renal pelvis > ureter > bladder

CT Urography Features:

Filling defect in renal pelvis or ureter during excretory phase
Enhancing soft-tissue mass contrasted against low-attenuation urine
Nephrographic/urothelial phase (60 sec) superior to excretory phase (5 min)
CTU sensitivity 97%, specificity 93% vs. gold standard retrograde pyelography

TCC ureter - enhancing mass in distal right ureter on CTU

Fig. TCC of ureter. (A,B) Enhancing mass in distal right ureter on CTU (arrows). (C) Antegrade pyelography: abrupt filling defect in ureter due to mass. - Grainger & Allison's

TCC ureter - filling defect right ureter on delayed CT urogram

Fig. TCC of ureter - filling defect in right ureter on delayed-phase CT urogram (arrows A,B). - Grainger & Allison's

3. Wilms' Tumour (Nephroblastoma)

Most common renal tumour in children (peak 3-4 years)
CT: large heterogeneous mass; enhances heterogeneously; claw of renal tissue
US: mixed echogenicity; may contain haemorrhage/necrosis
IVC thrombus in ~10%
Bilateral in 5-10%

4. Renal Lymphoma

Usually secondary (haematogenous spread)
CT patterns: multiple bilateral masses > solitary mass > perinephric soft tissue > diffuse infiltration
Homogeneous; minimal enhancement; "wrap around" renal vessels

5. Renal Metastases

Common primaries: lung, breast, colon, melanoma
Usually bilateral; small; minimal enhancement
CT: multiple hypoenhancing nodules

FLOWCHART: Approach to an Incidental Renal Mass

INCIDENTAL RENAL MASS DISCOVERED ON IMAGING
                    │
                    ▼
         Is it a CYST?
         (round; smooth; water attenuation ~0 HU; no enhancement)
           /              \
         YES               NO (solid or complex)
          │                │
          ▼                ▼
    Bosniak Classification   Does it contain FAT?
    (See table above)        (<-10 HU on unenhanced CT)
                              /         \
                            YES          NO
                             │           │
                             ▼           ▼
                     ANGIOMYOLIPOMA   Measure enhancement:
                                     Unenhanced → Nephrographic
                                           │
                      ┌──────────────────────────────────┐
                      │  >20 HU = DEFINITE ENHANCEMENT   │
                      │  10-20 HU = EQUIVOCAL             │
                      │  <10 HU = NO ENHANCEMENT          │
                      └──────────────────────────────────┘
                              │              │           │
                              ▼              ▼           ▼
                        NEOPLASM       MRI / Biopsy   Simple cyst
                     (RCC most likely)  to clarify    No follow-up
                              │
                              ▼
                      STAGING CT (chest/abdomen/pelvis)
                      ± MRI for IVC thrombus assessment
                              │
                  ┌───────────┴────────────────┐
                  ▼                            ▼
            Small (<3 cm)              Large / Complex
            Partial nephrectomy        Radical nephrectomy
            or ablation                (±IVC thrombectomy)

PART 2: IMAGING OF RENAL INFECTIONS AND COMPLICATIONS

Overview: Renal Infection Spectrum

RENAL INFECTION SPECTRUM (Ascending >> Haematogenous)
──────────────────────────────────────────────────────────────────
UNCOMPLICATED          COMPLICATED              SEVERE/SPECIAL
─────────────────      ───────────────────      ────────────────
Acute pyelonephritis   Renal abscess            Emphysematous
(imaging rarely        Perinephric abscess        pyelonephritis
needed)                Pyonephrosis             Xanthogranulomatous
                       Papillary necrosis         pyelonephritis
                                                Renal tuberculosis
                                                Fungal infection
──────────────────────────────────────────────────────────────────

When to Image in Renal Infection

IMAGING INDICATIONS IN PYELONEPHRITIS
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✘ NOT responding to antibiotics within 72 hours
✘ Unclear diagnosis
✘ Coexisting stone disease + possible obstruction
✘ Diabetes mellitus with poor response
✘ Immunocompromised patient
✘ Suspicion of abscess or complicated infection
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
MODALITY OF CHOICE: CT (nephrographic phase)

1. Acute Pyelonephritis (APN)

Imaging Findings:

Modality	Findings
US (often normal)	Loss of corticomedullary differentiation; focal/diffuse swelling; decreased echogenicity; Power Doppler: focal hypoperfusion
CE-CT (best test)	Wedge-shaped areas of decreased density (renal pyramid → cortex); streaky/striated nephrogram; focal or global swelling; perinephric fat stranding; Gerota's fascia thickening
MRI	Wedge-shaped T2 hyperintense zones; reduced enhancement; restricted diffusion on DWI
Scintigraphy (DMSA)	Photopenic defects in cortex (most sensitive for parenchymal involvement especially in children)

CT key: Sharp demarcation between diseased tissue and normally enhancing adjacent parenchyma during nephrographic phase. Streaky/striated nephrogram = pathognomonic.

2. Renal Abscess

FORMATION PATHWAY:
Pyelonephritis → Microabscesses → Coalescence → MACROABSCESS
                                                     │
                                           Rim of granulation tissue
                                                     │
                               Rupture through renal capsule
                                                     │
                                          PERINEPHRIC ABSCESS

Feature	Renal Abscess	Perinephric Abscess
US	Thick-walled hypoechoic/complex fluid; internal echoes/debris	Fluid collection surrounding kidney
CT	Rounded low-density mass; thick irregular rim enhancement; gas bubbles if gas-forming organism	Soft-tissue density collection in perinephric space; Gerota's fascia thickening; loculations
MRI	T2 hyperintense; T1 hypointense; DWI restricted	Similar pattern, extends beyond capsule
Treatment	Antibiotics ± CT-guided drainage	CT-guided drainage usually required

3. Pyonephrosis

Definition: Infected hydronephrosis - pus in an obstructed collecting system

Feature	Finding
US	Dilated collecting system with echogenic debris/layering; "dirty shadowing"; mobile debris
CT	Dilated pelvicalyceal system; high-attenuation debris; wall thickening; perinephric stranding
Gas	If gas-forming organism: echogenic foci with dirty shadowing (US); air in collecting system (CT)
Urgency	Medical emergency - needs urgent nephrostomy/drainage

4. Emphysematous Pyelonephritis (EPN)

Definition: Necrotising infection with gas in renal parenchyma; 90% in diabetics; high mortality without treatment

Class	CT Findings	Mortality	Treatment
Class I	Gas in collecting system only	Low	Antibiotics + drainage
Class II	Gas in renal parenchyma; no extension	Moderate	Antibiotics + drainage ± percutaneous
Class III A	Extension to perinephric space	High	Percutaneous drainage
Class III B	Extension to pararenal space	High	Percutaneous drainage
Class IV	Bilateral EPN or solitary kidney	Very high (>50%)	Emergency nephrectomy

CT = gold standard: mottled gas densities within renal parenchyma/collecting system; "bubbly" or "streaky" pattern

5. Xanthogranulomatous Pyelonephritis (XGP)

Definition: Chronic destructive infection; often secondary to staghorn calculus + obstruction; lipid-laden macrophages

XGP IMAGING CHARACTERISTICS
────────────────────────────────────────────────────────────────
• Enlarged, non-functioning kidney (90% unilateral)
• Central staghorn calculus (75% of cases)
• Focal (segmental) or diffuse replacement of parenchyma
• Multiple lipid-containing rounded low-density areas
  (xanthoma cells = fat density on CT!)
• Extension into perinephric fat and adjacent organs
• "Bear paw" sign: central high-density stone surrounded by
  multiple low-density masses (xanthoma nodules)
────────────────────────────────────────────────────────────────

Modality	Findings
Plain film / KUB	Staghorn calculus; enlarged renal shadow
US	Enlarged kidney; central echogenic calculus; hypoechoic masses; posterior shadowing
CT	BEST modality: central calculus; multiple water-density (−10 to +15 HU) rounded masses replacing parenchyma; extension into retroperitoneum
IVP	Non-functioning kidney ("silent kidney")

Differential: Must distinguish from renal TB and renal cell carcinoma.

6. Papillary Necrosis

Causes (Mnemonic: POSTCARDS)

Pyelonephritis
Obstruction
Sickle cell disease
Tuberculosis
Cirrhosis/analgesics
Analgesic nephropathy
Renal vein thrombosis
Diabetes mellitus
Sjogren's/shock

Modality	Findings
IVP / CT urography	Filling defect in calyx (necrotic papilla); "moth-eaten" calyx; "ring sign" (necrotic papilla surrounded by contrast); "lobster claw" or "ball on tee" deformity
US	Hypoechoic triangular area in medulla; papilla may be echogenic
CT	Hyperdense necrotic papilla (before sloughing); defect after sloughing; calyceal clubbing

PART 3: GENITOURINARY TUBERCULOSIS (GU TB)

Epidemiology

1.1-1.5% of all TB cases; 5-6% of extrapulmonary TB
Hematogenous seeding during primary pulmonary infection → renal cortex
High O₂ tension of cortex = favourable for M. tuberculosis
Men infected twice as often as women
Mean latent period from pulmonary TB to GU disease: 22 years (range 1-46 yrs)
Reactivation usually unilateral (bilateral in 25%)

Organ Involvement in GU TB:

Organ	Frequency
Kidneys	60-100%
Ureters	19-41%
Bladder	15-20%
Prostate/Epididymis	20-50% of men

Pathological Progression of Renal TB:

RENAL TB PATHOLOGICAL SEQUENCE
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Hematogenous seeding → Cortical granulomas (latent)
         │
         ▼
Caseating granulomas in cortex → CALYCEAL EROSIONS
(earliest imaging finding!)
         │
         ▼
PAPILLARY NECROSIS → cavitation of papillae
         │
         ▼
CALYCEAL CLUBBING + DILATION
         │
         ▼
HYDRONEPHROSIS (ureteric strictures)
         │
         ▼
RENAL PARENCHYMAL CAVITATION
         │
         ▼
DYSTROPHIC CALCIFICATION (granuloma → caseous necrosis → calcium)
         │
         ▼
AUTONEPHRECTOMY ("putty kidney" / "chalk kidney")
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Imaging Findings in GU TB (by Organ):

Kidney:

Stage/Feature	IVP	CT	US
Early: Calyceal erosions	Smudged, irregular calyces	Calyceal irregularity	Non-specific
Papillary necrosis	"Moth-eaten" appearance	Low-density papillary defects	Hypoechoic papillae
Cavitation	Cavities communicating with calyx	Parenchymal cavities with thick walls	Complex masses
Hydronephrosis	Dilated pelvicalyceal system	Dilated collecting system + strictures	Dilated PCS
Calcification	Stippled/dystrophic calcium	Cortical/curvilinear/putty calcification	Echogenic foci + shadowing
Autonephrectomy	Non-functioning kidney	Shrunken, calcified, non-enhancing kidney	Small hyperechoic kidney

Ureter:

Feature	Imaging Appearance
Ureteric strictures	Multiple; irregular; "pipe-stem ureter"
Beading	Alternating strictures + dilatations
"Golf-hole" ureter	Short, straight, wide ureteric orifice on cystoscopy
Location	Often distal ureter first; may progress proximally
CT	Thickened ureteric wall; irregular lumen; peritubular stranding

Bladder:

Feature	Imaging
Cystitis/thickening	Wall thickening (US, CT)
"Thimble bladder"	Severely contracted, fibrotic bladder on CT/IVP
Calcifications	Bladder wall calcification on CT
Capacity	Markedly reduced volume

Male Genital TB:

Organ	Finding
Epididymis	Enlarged, heterogeneous; calcifications; "beaded" on US
Prostate	Nodular/granulomatous; elevated PSA - mimics PCa
Vas deferens	Thickened, "beaded" appearance on US
Testis	Non-tender mass; complex epididymo-orchitis

CT vs. IVP in GU TB:

Feature	IVP	CT
Currently preferred?	No (historical standard)	YES (now preferred)
Detects calcification	Moderate	Excellent
Shows cavitation	Poor	Excellent
Ureteric detail	Good (with retrograde)	Good
Extraurinary spread	No	Excellent (lymph nodes, adrenal)
Non-functioning kidney	Silent/white out	Can assess residual parenchyma
Follow-up during Rx	IVP every 6 months for ureteric strictures	CT when indicated

GU TB Key Imaging Signs:

GU TB IMAGING SIGNS SUMMARY
─────────────────────────────────────────────────────
KIDNEY
  • "Moth-eaten" calyces = papillary necrosis (earliest)
  • "Phantom calyx" = amputation of infundibulum
  • "Putty kidney" = totally calcified autonephrectomy
  • "Lobar nephronia" = focal parenchymal destruction

URETER
  • "Pipe-stem" ureter = rigid, strictured ureter
  • "Saw-tooth" ureter = multiple strictures
  • "Golf-hole" ureteric orifice = cystoscopy finding

BLADDER
  • "Thimble bladder" = contracted fibrotic bladder

EPIDIDYMIS
  • "Beaded epididymis" = multiple granulomas
─────────────────────────────────────────────────────

Diagnostic Algorithm for Suspected GU TB:

SUSPECTED GU TB
(sterile pyuria + haematuria + relevant history)
              │
              ▼
    3x early morning urine for AFB culture
    (positive in 75-90% of active cases)
              │
              ▼
         CT ABDOMEN/PELVIS
    (preferred over IVP)
              │
        ┌─────┴───────────────────────────┐
        ▼                                 ▼
  CHARACTERISTIC FINDINGS           NON-DIAGNOSTIC
  (calyceal erosion, calcification,       │
   strictures, cavitation)                ▼
        │                          TISSUE BIOPSY ±
        ▼                          PCR of urine
  CONFIRM with culture/PCR
        │
        ▼
  TREATMENT:
  4-drug regimen (HRZE × 2 months)
  → 2-drug (HR × 4 months)
        │
        ▼
  FOLLOW-UP IVP every 6 months
  (detect new ureteric strictures!)
        │
        ▼
  Ureteric obstruction developing?
        │
    YES ┤
        ▼
  Balloon dilation / stent / reimplantation
  (corticosteroids do NOT prevent)

Complications of GU TB and Their Management:

Complication	Imaging	Management
Ureteric stricture	CT/IVP: obstruction + hydroureter	Balloon dilation; ureteral stent; reimplantation
Hydronephrosis	US/CT: dilated PCS	Nephrostomy if infected; drainage
Autonephrectomy	CT: shrunken calcified kidney	Nephrectomy (pain, hypertension, drug resistance)
Thimble bladder	CT: tiny contracted bladder	Bladder augmentation surgery
Fistula	CT/fistulograms	Surgical repair
Renal failure	CT small kidneys bilaterally	Dialysis/transplant

Fungal Urinary Tract Infection (Special Mention)

Usually Candida species (C. albicans >50%)
Risk: ICU, immunocompromised, indwelling catheters, broad-spectrum antibiotics
Imaging:
- US/CT: filling defects in collecting system = fungus balls (echogenic masses without shadowing)
- Bladder: focal wall thickening
- Can cause hydronephrosis if fungus ball obstructs UPJ or ureter

Summary Comparison Table: Complicated Renal Infections

Condition	Key CT Finding	Key Risk Factor	Treatment
Acute APN	Wedge-shaped nephrogram defect	UTI	Antibiotics
Renal abscess	Thick rim-enhancing fluid collection	DM; IV drug use	Antibiotics ± drainage
Perinephric abscess	Perinephric fluid + gas	Ruptured renal abscess	CT-guided drainage
Pyonephrosis	Dilated PCS + debris + gas	Obstruction + UTI	Emergency nephrostomy
Emphysematous PN	Gas in renal parenchyma	Diabetes (90%)	Drainage ± nephrectomy
XGP	Staghorn calculus + fat-density masses	Staghorn stone	Nephrectomy
Papillary necrosis	"Moth-eaten" calyces; "ring sign"	DM, analgesics, sickle cell	Treat underlying cause
Renal TB	Calyceal erosion → calcification	Prior pulmonary TB	HRZE × 2 mo + HR × 4 mo
Fungal infection	Fungus ball in collecting system	Immunosuppression	Antifungals ± drainage

Quick Reference: Imaging Modality of Choice

Clinical Scenario	First Choice	Second Choice
Incidental renal mass	CT (multiphase)	MRI
Fat-containing renal mass	CT unenhanced	MRI chemical shift
Complex cyst characterisation	CT (Bosniak)	MRI
TCC / urothelial tumour	CT Urography	Retrograde pyelography
RCC staging / IVC thrombus	CT + MRI	CT alone
Uncomplicated pyelonephritis	None needed	US (if obstruction suspected)
Complicated pyelonephritis	CE-CT (nephrographic phase)	US
Emphysematous pyelonephritis	CT	CT (no alternative)
XGP	CT	US + plain film
GU Tuberculosis	CT	IVP (follow-up for strictures)
Renal calculi acute	Unenhanced CT (low-dose)	US + KUB
Pregnancy + suspected stone	MRI urography	US
Renal failure - size/obstruction	US	Unenhanced CT

Key Textbook References:

Grainger & Allison's Diagnostic Radiology (Chapter 26 - Uroradiology), pp. 719-734

Brenner & Rector's The Kidney (Chapter 25 - Renal Imaging), pp. 1107-1120; Chapter 36 - Renal Infection, pp. 1644-1650

Campbell Walsh Wein Urology (Chapter 32 - Genitourinary Tuberculosis)

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