Intravenous Urography (IVU)
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Direct answer
An intravenous urogram (IVU, also IVP) begins with a plain control film of the abdomen, followed by intravenous iodinated contrast (about 50-100 mL of a 300 mg iodine per mL non-ionic agent in an average adult) with a sequence of timed films: a nephrogram effect within the first minute, pyelograms at about 5 minutes, ureteric compression released at 10-15 minutes, a full-bladder film around 15-20 minutes, and a post-micturition view. Obstruction is pursued with delayed films — hours, even up to a day — because a hydronephrotic kidney drains late. Renal function and previous reactions are checked beforehand, and although ultrasound and CT urography have largely replaced IVU in modern Indian practice, its timed logic remains a favourite examination topic.
What you must remember
- Always a plain control film first: calculi and calcifications must be identifiable before contrast hides them; comparison before-and-after is the whole point.
- Contrast dose: roughly 1 mL per kg (50-100 mL of 300 mgI/mL non-ionic agent) in adults; renal excretion is by glomerular filtration — no tubular concentration step.
- Nephrogram phase (about 30-60 seconds after injection): cortical uptake at its densest — the best phase for renal size, contour and scarring.
- Pyelogram phase (about 5 minutes): pelvicalyceal filling; ureteric compression (a paddle over the iliac crests) holds contrast in the collecting system for detail.
- Compression is contraindicated with abdominal aortic aneurysm, abdominal mass, recent abdominal surgery, renal transplant or a solitary kidney — use a 10-15 degree head-down tilt instead.
- Delayed films (1-24 hours in obstruction) show a dense, slowly clearing kidney; a "negative total" phase (staghorn calculus, obstruction) may show only a persistent nephrogram.
- Preparation traditionally includes low-residue diet and a laxative the previous evening; strict dehydration is no longer advised — infants, diabetics and patients with myeloma or renal impairment must be well hydrated.
- Modern context: ultrasound and non-contrast CT have displaced IVU for stones, and CT urography for haematuria — but the technique, timing and complications remain examinable.
A full IVU run, timed
Sit at the console with the clock and the sequence makes sense. Zero minutes: the control KUB — look for calculi along the urinary tract line and note phleboliths to distinguish later. Injection of non-ionic contrast, flushed with saline. One minute: the nephrogram — both kidneys should blush equally; an absent nephrogram on one side is arterial occlusion, a non-functioning kidney, or delayed filling to come. Five minutes: pyelograms — calyces should be crisp with sharp fornices; blunted calyces, clubbed fornices and a dilated pelvis indicate obstruction, which may be partial (the affected side denser and later).
At 10-15 minutes, release the compression paddle (or remove the tilt): the contrast column runs down the ureters, and obliques can separate ureter from overlapping bone; the level of a stopping column localises an obstruction. A 15-20 minute full-bladder film outlines the bladder; the post-micturition film reveals residual urine and completes the study in a patient who can void.
Now the branch point examiners probe. The right kidney's pyelogram never appears by 20 minutes — do not discharge the patient. A delayed film at 1, 2, even 6 or 24 hours may show a hydronephrotic collecting system filling from above, proving the obstruction's level, and modern practice would move the patient to CT at this point. The IVU is not a fixed set of films but a logic tree on a clock — and knowing which branch to take at which minute is the skill the examination is really testing.
Where students slip
Forgetting the control film leads the list — every contrast study in the urinary tract begins plain. Second, compression: candidates apply it by protocol without asking the contraindications; an aneurysm compressed by a paddle is a memorable error. Third, the timing of the phases gets garbled: nephrogram under a minute (cortical blush), pyelogram around five minutes (collecting system), delayed films only when drainage fails — the numbers themselves are asked as one-liners. Fourth, "no fluids before IVU" is quoted blindly; dehydration is dangerous precisely in the patients who need renal protection — infants, diabetics, myeloma and renal impairment.
Frequently asked questions
Why is a control film taken before contrast injection?
To demonstrate calculi, calcifications and renal outlines that contrast can later obscure, and to check exposure, preparation and bowel gas before committing the patient to contrast.
What are the nephrogram and pyelogram phases?
The nephrogram is the dense cortical blush within the first minute; the pyelogram at about five minutes shows pelvicalyceal filling once contrast reaches the collecting system.
When is ureteric compression used and when is it contraindicated?
Compression above the iliac crests holds contrast in the upper tracts for better filling; it is contraindicated in aortic aneurysm, abdominal masses, recent surgery and renal transplants — replaced by a head-down tilt.
Why are delayed films taken in obstruction?
A chronically obstructed kidney fills slowly, so films at 1 to 24 hours demonstrate the dilated system and the level of the blockage that early films miss.