Intravenous Urography

Intravenous urography (IVU, intravenous pyelography) is a radiographic study of the kidneys, collecting systems, ureters and bladder after an intravenous injection of water soluble iodinated contrast.

The usual dose is 50 to 100 mL of a low osmolar non-ionic agent, 300 to 370 mg of iodine in each mL. In children it is 1 mL for each kg up to a maximum.

A control film of the kidneys, ureters and bladder (KUB) is taken first, followed by films at timed intervals:

• A nephrogram film at 1 to 5 minutes.
• Films at 5, 10 and 15 minutes showing the calyces and ureters, with tomograms or abdominal compression if required.
• A full length film and a post-micturition film.

Delayed films at 30 minutes to 24 hours are taken in obstruction.

The effective dose is about 3 to 5 mSv.

Intravenous urography was the first line test for haematuria, renal colic and urinary tract abnormalities for decades. Ultrasound, non-contrast low dose CT (the first line test for renal colic), CT urography and MR urography have replaced it in most centres, because they show more of the kidneys and surrounding structures with greater accuracy.

IVU is still used where CT is unavailable, for follow up of known urinary tract disease after surgery, and for detailed anatomy of the ureters and collecting system.

Indications. Haematuria (visible, or non-visible in a patient at risk), after ultrasound and cystoscopy, if CT urography is not available. Renal colic when CT is unavailable, to confirm obstruction and level. Recurrent urinary tract infection with suspected structural abnormality. Suspected urothelial tumour of the upper tract.

Congenital anomalies (duplex system, horseshoe kidney, pelviureteric junction obstruction, ureterocele). Renal trauma or ureteric injury when CT is not available. Assessment of ureters after pelvic surgery. Follow up of urinary diversion (ileal conduit). Not for routine assessment of renal function or hypertension, and not in acute kidney injury.

Contraindications and precautions. Previous severe reaction to iodinated contrast (anaphylaxis, bronchospasm): avoid, or use premedication and a different agent. Impaired renal function (eGFR under 30 mL each minute for 1.73 m2): the study gives poor images and risks contrast nephropathy, so ultrasound or non-contrast CT or MR is chosen.

Metformin: withheld for 48 hours after the study if eGFR is under 30 or in acute kidney injury. Dehydration, multiple myeloma and diabetic nephropathy: increase the risk of contrast nephropathy; ensure hydration. Pregnancy: avoid. Active thyrotoxicosis (iodine load). Compression is avoided in suspected obstruction, abdominal mass, aneurysm, recent surgery or trauma.

Resuscitation equipment and trained staff must be present.

Preparation and technique. No special preparation is usual: a light diet, laxatives in some departments to reduce bowel gas (not in children), and good hydration. The patient empties the bladder, a control film is taken, contrast is injected as a bolus or short infusion, and timed films are taken.

A prone film distends the ureters, tilted films show a pelviureteric junction, and a post-micturition film shows bladder emptying. Delayed films are taken until the level of obstruction is shown.

Normal appearances. The control film shows two kidneys (9 to 13 cm long, the left slightly higher than the right, each about 3 vertebral bodies in length), psoas outlines, and no calcification along the urinary tract.

After injection, a dense nephrogram appears within 1 minute, and symmetrical contrast fills the sharply cupped calyces (7 to 14 in each kidney), the infundibula and the pelvis by 5 minutes. The ureters (3 to 4 mm wide) are seen in segments because of peristalsis, with smooth walls and three physiological narrowings (the pelviureteric junction, the pelvic brim and the vesicoureteric junction).

The bladder is smooth with a capacity of 300 to 500 mL, and empties completely after voiding, with a post-micturition residue under 50 mL. The renal parenchymal thickness is 2 to 2.5 cm, and kidneys move 2 to 3 cm with respiration.

Interpretation.

• Obstruction: delayed, prolonged and increasingly dense nephrogram, delayed excretion of contrast, dilatation of the pelvis and calyces with a ureter dilated down to the point of obstruction, and a "column" of contrast stopping at a stone. Delayed films show the level.
• A calculus at the pelviureteric junction, the pelvic brim or the vesicoureteric junction is the commonest cause. A persistent "standing column" shows partial obstruction.
• Calculi: radio opaque stones on the control film (calcium oxalate and phosphate stones, 80 to 85%) and filling defects of lucent stones (uric acid) on contrast films; staghorn calculi fill the pelvicalyceal system.
• Papillary necrosis: clubbed calyces, "ball on tee" and "lobster claw" signs, with sloughed papillae (diabetes, analgesic nephropathy, sickle cell disease, obstruction).
• Renal tuberculosis: a calyceal erosion with a "moth eaten" appearance, parenchymal scars and calcification (putty kidney), a beaded ureter ("pipe stem") with strictures, and a small thimble bladder.
• Tumours: renal cell carcinoma distorts or displaces the calyces (stretched, amputated, splayed) and enlarges the renal outline; transitional cell carcinoma shows an irregular filling defect ("goblet" sign for a ureteric lesion with a dilated segment distal to it) or an irregular wall.
• Congenital anomalies: duplex collecting system (the "drooping lily" appearance when an obstructed upper moiety displaces the lower moiety), ectopic ureter, and ureterocele ("cobra head" or "spring onion" sign).
• Other congenital anomalies: horseshoe kidney (joined lower poles with medially directed lower calyces), pelvic kidney, and pelviureteric junction obstruction (a dilated pelvis with a normal ureter).
• Reflux nephropathy: focal cortical scarring with clubbed calyces over the scar (reflux scarring, usually at the poles).
• Polycystic and cystic disease: enlarged kidneys with stretched, elongated calyces ("spider leg"), and multiple cysts displacing the pelvicalyceal system; medullary sponge kidney shows "paintbrush" tubular blush.
• Renal artery stenosis, abnormal or delayed nephrogram, and small smooth kidneys in chronic disease: the test is neither sensitive nor specific.
• Bladder: filling defects (tumour, stone, blood clot, prostate enlargement impressing the base), trabeculation and diverticula (obstruction), and incomplete emptying.
• Trauma: extravasation of contrast around the kidney, absent function (an avulsed pedicle), or ureteric injury with a leak.
• Ileal conduit: reflux, stenosis at the ureteroileal anastomosis, and stones.

Critical values and findings needing immediate action.

• Anaphylaxis or severe contrast reaction (urticaria, bronchospasm, hypotension, laryngeal oedema): stop the injection, give intramuscular adrenaline, oxygen, intravenous fluids, and call for resuscitation support.
• Obstruction with infection (fever, rigors, pyonephrosis): urgent decompression by nephrostomy or ureteric stent, with antibiotics.
• Complete obstruction of a solitary kidney or bilateral obstruction with rising creatinine: urgent drainage.
• Contrast extravasation after trauma with haemodynamic instability: resuscitation, CT and urological or surgical review.
• Findings of a renal mass or urothelial tumour: urgent staging, cystoscopy and urology referral.
• Contrast extravasation with a suspected ureteric injury: urgent urological review.

Limitations and artefacts.

• Poor visualisation from bowel gas, faeces, barium from earlier studies, obesity, and impaired renal function can hide stones and masses; CT or ultrasound are more reliable.
• The study is insensitive for small renal masses (under 3 cm) and cannot separate cysts from solid tumours, and ultrasound, CT or MR is needed for characterisation.
• Contrast nephropathy: a rise in creatinine of 0.5 mg in each dL (44 micromol in each litre) or 25% within 48 to 72 hours, with risk factors of diabetes, renal impairment, dehydration, myeloma and nephrotoxic drugs; hydration reduces risk.
• Contrast reactions: mild (nausea, flushing, urticaria) in 1 to 3% of non-ionic injections, severe reactions in about 1 in 10 000 to 1 in 40 000; delayed rash up to a week; extravasation at the injection site causes pain and swelling.
• The test does not measure split renal function; isotope renography is needed for this.
• Normal variants (foetal lobulation, dromedary hump, a prominent column of Bertin, ureteric kinks) mimic disease; tomography or ultrasound clarifies.
• A normal IVU does not exclude a small ureteric stone, urothelial tumour, or early disease.
• Radiation dose is moderate and comparable to CT of the abdomen at low dose, so ultrasound is chosen first for most indications.

Special groups.

• Children: ultrasound and isotope scans are preferred, with IVU kept for anatomical detail, with the contrast dose scaled to weight.
• Pregnancy: avoid; ultrasound and MR urography without contrast are used.
• Patients with renal impairment, diabetes or myeloma: avoid contrast, or hydrate and withhold nephrotoxic drugs and metformin.
• Patients on metformin: follow the local rule for stopping metformin after contrast.
• Patients with asthma and previous reactions: higher risk of reactions; premedication does not remove the risk.
• Regions: urinary schistosomiasis (bladder wall calcification, ureteric strictures, hydronephrosis, and bladder cancer), renal tuberculosis, stone disease, and obstructive uropathy from prostate disease or cervical cancer are common, and IVU may be the only contrast study available.

Follow up tests.

• Imaging: ultrasound of the kidneys and bladder, non-contrast low dose CT of the urinary tract, CT urography, MR urography, and isotope renography (technetium mercaptoacetyltriglycine) for function and drainage.
• Endoscopy and contrast studies: cystoscopy, ureteroscopy and retrograde pyelography.
• Urine: culture, microscopy and cytology, and urine for schistosome eggs.
• Blood and stone studies: serum creatinine and electrolytes, calcium, uric acid, and urinary stone risk studies.
• Referral to urology or nephrology.