What is a retrograde pyelogram, including its indications, contraindications, technique, complications, and alternative imaging options?

Retrograde Pyelogram: Definition, Indications, and Clinical Application

What is a Retrograde Pyelogram?

A retrograde pyelogram (RPG) is an invasive fluoroscopic procedure in which water-soluble contrast is injected in a retrograde fashion through a ureteral catheter into the ureter and renal collecting system to provide detailed visualization of the upper urinary tract anatomy. 1

The procedure requires specialized equipment including fluoroscopy, an operating room with radiation-shielded walls, and a C-arm compatible table, and must be performed by a urologist or trained specialist. 2

---

Primary Indications

Intraoperative Ureteral Injury (Gold Standard)

• RPG is the gold-standard diagnostic method for suspected iatrogenic ureteral injury during surgery and should be performed intraoperatively when injury is suspected. 2
• Direct visual inspection of the ureters is mandatory during emergency laparotomy; if standard positioning is not feasible, a cystotomy for retrograde catheter placement may be employed. 2

Trauma Evaluation

• RPG is recommended when CT is unavailable or contraindicated for assessing traumatic injury to the urinary tract. 2, 1

Upper Tract Urothelial Malignancy

• RPG should be considered in patients with positive urinary cytology but negative cystoscopy, combined with prostatic urethral biopsies, enhanced cystoscopy, ureteroscopy, or random bladder biopsies to identify the source of malignant cells. 2
• RPG provides detailed visualization of renal pelvic or ureteral tumors, especially to locate the origin of positive cytology. 2

Renal Insufficiency with Contraindication to IV Contrast

• When intravenous contrast is contraindicated due to renal insufficiency or prior severe allergic reactions, RPG provides contrast-enhanced evaluation without systemic iodine exposure. 2
• Gadolinium-based contrast agents (gadobenate dimeglumine diluted 50:50 with saline) can serve as an effective alternative to iodinated contrast in patients with documented iodine allergy. 3

Assistance with Interventions

• RPG aids in stent placement, ureteroscopy guidance, and identification of stones or tumors when cross-sectional imaging is inadequate. 1

---

Contraindications and Precautions

Active Urinary Tract Infection

• RPG should be performed with caution in the setting of active infection due to risk of bacteremia and sepsis. 2

Bilateral Procedures Require Extreme Caution

• Bilateral RPG in the same sitting can cause acute renal shutdown and anuria, particularly in patients with baseline renal insufficiency. 4
• A case report documented a patient with baseline creatinine 1.9 mg/dL who developed anuria and required three sessions of hemodialysis after bilateral RPG using 6 mL of meglumine diatrizoate per side. 4
• If bilateral evaluation is necessary, consider staging the procedures or routine double-J stenting, though this approach requires further study. 4

Urethral Injury

• Retrograde urethrography must be performed before attempting catheterization if urethral injury is suspected (blood at meatus, inability to pass catheter easily, perineal ecchymosis). 5, 2

---

Procedural Technique

Pre-Procedure Steps

• Perform comprehensive cystoscopic examination of the urethra and bladder before RPG, documenting tumor size, location, configuration, number, and mucosal abnormalities. 2
• Obtain retrograde urethrography first if urethral injury is suspected to avoid exacerbating the disruption. 2

Contrast Administration

• Use water-soluble contrast (typically meglumine diatrizoate or iohexol) injected through a 5-Fr universal ureteral catheter under fluoroscopic guidance. 1, 4
• For patients with iodine allergy, gadobenate dimeglumine diluted 50:50 with saline provides adequate opacification, though radiographic quality is inferior to iodinated contrast. 3
• Typical volume is 6-10 mL per side, with careful monitoring to avoid excessive pressure and pyelosinus/venous/lymphatic reflux. 4

Monitoring During Procedure

• Patients must be observed for hypotension, hypoxia, or allergic manifestations indicative of contrast reaction. 2

---

Post-Procedure Monitoring

• Check serum creatinine on postoperative day 1 after bilateral RPG or in any patient with pre-existing renal impairment. 2, 4
• Monitor urine output closely, as anuria can develop in the immediate postoperative period, particularly after bilateral procedures. 4

---

Complications

Acute Renal Failure

• Bilateral RPG carries risk of acute renal shutdown, especially in patients with baseline renal insufficiency (creatinine >1.5 mg/dL). 4

Infection and Sepsis

• Retrograde instrumentation can introduce bacteria into the upper urinary tract, particularly in patients with existing bacteriuria. 2

Contrast Reactions

• Allergic reactions to iodinated contrast can occur, though severe reactions are uncommon in nonvascular urologic procedures. 3

Ureteral Perforation or Injury

• Catheter manipulation can cause iatrogenic injury, particularly in the presence of strictures or anatomic abnormalities. 1

---

Alternative Imaging Options

CT Urography (Preferred for Most Indications)

• Contrast-enhanced CT of the abdomen and pelvis has largely replaced RPG for diagnostic purposes, with 90-92% accuracy for detecting upper tract pathology. 5, 2
• CT is superior to RPG for detecting urolithiasis, emphysematous pyelonephritis (gas detection), and parenchymal abnormalities. 5
• CT provides comprehensive evaluation of the entire genitourinary tract without the invasiveness of RPG. 5

MRI Urography

• MRI combined with RPG provides an alternative for patients with contraindications to CT, though MRI has poor accuracy for detecting small ureteral calculi and reduced ability to detect gas. 5, 2
• Diffusion-weighted imaging (DWI) can detect pyelonephritis, abscesses, and pyonephrosis without contrast. 5

Ultrasound

• Ultrasound is preferred in pregnant patients to minimize radiation exposure and can be combined with RPG when necessary. 2
• Ultrasound has limited ability to detect parenchymal abnormalities (40% detection rate vs 84.4% for CT). 5

Antegrade Pyelography

• Antegrade pyelography via percutaneous nephrostomy is not beneficial for initial evaluation but may be useful when RPG is technically unsuccessful. 5, 1

---

Modern Role in Clinical Practice

RPG is NOT Indicated For:

• Initial evaluation of uncomplicated pyelonephritis—imaging is not required in patients who respond appropriately to antibiotics within 72 hours. 5, 2
• Routine follow-up of incompletely opacified ureteral segments on CT urography when the ureters appear otherwise normal and there is no hydronephrosis (yield only 2.7% for detecting abnormalities, 1.4% for cancer). 6
• Acute evaluation of vesicoureteral reflux—voiding cystourethrography (VCUG) is performed after resolution of acute symptoms. 5

RPG Remains Essential For:

• Intraoperative diagnosis of suspected ureteral injury (gold standard). 2
• Detailed collecting system visualization when cross-sectional imaging is inadequate or contraindicated. 2, 1
• Guidance for therapeutic interventions (stent placement, ureteroscopy) when anatomy is unclear. 1

---

Common Pitfalls to Avoid

• Never perform bilateral RPG in the same sitting without careful consideration of renal function and strong clinical indication—stage procedures when possible. 4
• Do not attempt bladder catheterization before obtaining retrograde urethrography if urethral injury is suspected. 5, 2
• Avoid relying on RPG for routine diagnostic purposes when non-invasive CT or MRI can provide equivalent or superior information. 5, 6
• Do not perform RPG to follow up incompletely opacified ureteral segments on CT urography if the ureters appear otherwise normal—the yield is extremely low (2.7%). 6
• Ensure adequate fluoroscopic equipment and urologic expertise are available before attempting the procedure. 2