Intravenous Pyelogram (IVP) - Comprehensive Overview

Definition

Historical Context

Anatomy Assessed

• Kidneys - size, shape, position, cortical outline, nephrographic density
• Collecting system - calyces, infundibula, renal pelvis
• Ureters - course, caliber, filling defects, strictures
• Urinary bladder - outline, capacity, filling defects, post-void residual

IVP X-ray - 10-Minute Excretory Phase

Indications

1. Hematuria (gross or microscopic) - evaluating the source
2. Flank or loin pain - suspected ureteral stone or obstruction
3. Urinary calculi - especially when dynamic imaging of obstruction is needed; detects radiolucent stones as filling defects (sensitivity ~75%, specificity >90%)
4. Congenital anomalies - horseshoe kidney, duplex collecting system, ectopic kidney, UPJ obstruction
5. Urothelial tumors - uroepithelial neoplasms of the renal pelvis, ureter, and bladder
6. Urinary tuberculosis - characteristic changes (see below)
7. Renal scarring and pyelonephritis - papillary necrosis, cortical scarring
8. Hydronephrosis and obstruction - when dynamic excretion data is required
9. Medullary sponge kidney - characteristic medullary ectasia with staining
10. Post-intervention follow-up - after ureteroscopy, nephrolithomy, or pyeloplasty
11. Enlarged prostate - bladder indentation, post-void residual
12. Urethral/ureteral strictures

Note: IVP remains relevant when CT with contrast is unavailable and when dynamic upper tract excretion/obstruction imaging is specifically needed. More than 70% of urinary stones are radio-opaque, so plain KUB can assist follow-up once a stone is identified.

Patient Preparation

• Bowel preparation: Mild laxative the evening before to reduce overlying bowel gas (controversial; based on preference)
• Fasting: Typically NPO after midnight (reduces bowel gas, but strict dehydration is no longer advocated)
• Avoid dehydration in: infants, elderly, debilitated patients, diabetics, renal failure, multiple myeloma, hyperuricemia (risk of contrast nephropathy)
• Allergy history: Ask specifically about prior reactions to iodinated contrast
• Renal function: Check serum creatinine before contrast administration
• Pregnancy: Contraindicated - radiation and contrast both pose risk
• Metformin: Withhold for 48 hours around iodinated contrast in diabetics with risk of renal impairment

Standard Technique - Step-by-Step

Step 1: Scout Film (KUB - Kidneys, Ureters, Bladder)

• Identifies pre-existing radio-opaque calcifications (renal, ureteral stones, nephrocalcinosis, vascular calcifications)
• Establishes a baseline for comparison
• Shows psoas shadows, renal outlines, and bowel gas pattern

Step 2: Contrast Injection

• Iodinated contrast (ionic or non-ionic) is injected IV, typically into an antecubital vein
• Non-ionic low-osmolar contrast is preferred (fewer reactions)
• The contrast flows through the renal vasculature and is filtered into the collecting system, opacifying it on X-ray

Step 3: Nephrogram Phase (Immediate / 1 min)

• Immediate film (taken right after bolus injection)
• Kidney parenchyma appears densely opaque = "nephrogram"
• Assesses renal size, shape, cortical outline, position
• Both kidneys should appear symmetrically within 1 minute

Step 4: Early Pyelogram Phase (5-10 min)

• Calyces, infundibula, and renal pelvis begin to fill
• Best phase for assessing the collecting system anatomy
• Calyceal details, filling defects, papillary necrosis visible here
• Ureteral peristalsis becomes visible

Step 5: Excretory/Urographic Phase (10-15 min)

• Full visualization of the ureters from renal pelvis to vesicoureteric junction
• Bladder begins to fill
• Oblique films may be taken to profile the ureters away from bony overlap

Step 6: Bladder Phase (15-20 min)

• Full bladder outline assessed
• Indentations (enlarged prostate, pelvic mass, tumor) detected

Step 7: Post-Void Film

• Patient voids, then a final film is taken
• Assesses post-void residual volume
• Detects bladder neck obstruction, residual ureteral contrast, or reflux

Modifications / Special Techniques

Radiographic Interpretation - Systematic Assessment

Kidneys

• Size: Normal adult kidney = 11-14 cm pole-to-pole; each should be within 1.5 cm of the other
• Position: Upper pole at T12, lower pole at L3
• Outline: Smooth contour; lobulated (fetal lobulation) vs. scar indentation
• Nephrogram density: Symmetric and dense; asymmetry may indicate reduced function on one side

Collecting System

• Calyces: Sharp, cupped; blunting = early obstruction; clubbing = established hydronephrosis
• Papillary necrosis: "Signed ring" or "lobster claw" appearance at papillary tips
• Filling defects: Blood clot, tumor, radiolucent stone, fungal ball

Ureters

• Caliber: Should not exceed 5 mm (up to 7 mm at UVJ)
• Course: Medial deviation (retroperitoneal fibrosis), lateral deviation (lymph node mass)
• Filling defects: Stone, tumor, blood clot
• Stricture: Smooth tapered narrowing vs. irregular (malignancy)

Bladder

• Outline: Smooth, round; asymmetric indentation = prostatic impression, pelvic mass
• Filling defect: Tumor, stone, blood clot
• "Christmas tree" bladder: Neurogenic bladder

IVP Findings in Specific Conditions

Urinary Tuberculosis (classic IVP findings)

1. Minimal calyceal dilation and loss of sharpness (early change)
2. Irregular, "moth-eaten" calyx
3. Calyceal erosion and "phantom calyx"
4. Upward-pointing "hiked-up" pelvis
5. Kerr's kink sign - kinking of renal pelvis
6. Corkscrew ureter - areas of stricture and dilation
7. Pipestem ureter - diffusely thickened
8. Distal ureteric narrowing at ureterovesical junction
9. Thimble bladder - small capacity, thick-walled

Urinary Calculi

• Radio-opaque stones: calcium oxalate, calcium phosphate, struvite (magnesium ammonium phosphate), cystine
• Radiolucent stones: uric acid, xanthine, triamterene - seen as filling defects on IVP
• IVP sensitivity ~75%, specificity >90% for calculi
• Obstructing stones: delayed nephrogram, dilated collecting system proximal to stone

Renal Obstruction

• Delayed or dense nephrogram persisting >5 min = obstruction
• Dilated calyces and pelvis proximal to point of obstruction
• "Standing column" of contrast in ureter = no peristalsis = obstruction

Papillary Necrosis

• Ring shadow around necrotic papilla ("lobster claw" sign)
• Sloughed papilla = triangular filling defect in calyx

Medullary Sponge Kidney

• Linear "paintbrush" striations in the medullary pyramids
• Medullary calcifications clustered around calyces

Hydronephrosis

• Dilated calyces, pelvis, and ureter
• Cortical thinning with severe longstanding obstruction

Contraindications

Complications

1. Contrast reactions:
   • Mild: urticaria, nausea, vomiting, flushing, metallic taste (most common)
   • Moderate: bronchospasm, facial edema, hypertension/hypotension
   • Severe: anaphylactic shock (rare, ~1 in 10,000-40,000)
   • Pre-medication for known mild reactions: oral corticosteroid + antihistamine 12-13 hours before
2. Contrast nephropathy: Transient or permanent AKI, especially in pre-existing CKD, diabetes, dehydration
3. Extravasation: Local tissue irritation at injection site
4. Radiation exposure: More than a plain radiograph, less than a standard CT scan

IVP vs. Modern Alternatives

• CT is unavailable or the patient cannot have CT contrast
• Dynamic excretion/obstruction imaging is specifically required
• Demonstrating small lesions: papillary necrosis, medullary sponge kidney, pyeloureteritis cystica, small urothelial tumors
• Resource-limited settings for urinary stones and TB (widely available, lower cost, lower radiation than CT)

Summary