Hydronephrosis in Cattle: Swollen Kidney From Urinary Obstruction

Hydronephrosis is swelling and stretching of the kidney's urine-collecting area because urine cannot flow out normally. Over time, that pressure can thin and damage kidney tissue. In cattle, this may affect one kidney or, less commonly, both. If only one kidney is involved, the problem can be easy to miss early on because the other kidney may keep working.

Hydronephrosis is not a disease by itself. It is a result of another problem, most often urinary obstruction. That obstruction may happen in the ureter, bladder outlet, or urethra. In cattle, urinary stones and lower urinary tract blockage are important causes, especially in males, while chronic infection, scarring, masses, or congenital abnormalities can also play a role.

The outlook depends on how long the blockage has been present and whether kidney tissue is still functional. A short-lived partial blockage may improve if your vet can relieve the cause. A long-standing obstruction can leave the kidney permanently enlarged and poorly functional, even after the urine flow problem is addressed.

The most common cause is urinary obstruction. In cattle, that often means uroliths, also called urinary stones, that form in the bladder and lodge farther down the tract. Merck notes that in cattle and other ruminants, stones commonly develop in the bladder and can obstruct urine flow, especially in males. When urine backs up long enough, the pressure can dilate the renal pelvis and damage the kidney.

Infection is another important cause. Ascending urinary tract infection can inflame and scar the bladder, ureters, or kidney. In cattle, pyelonephritis can cause blood in the urine, straining, fever, and kidney damage. Chronic inflammation may narrow urine outflow enough to contribute to hydronephrosis.

Less common causes include tumors or masses compressing the ureter, trauma, pregnancy-related compression, adhesions, or congenital defects present from birth. Some cattle are found to have hydronephrosis incidentally on ultrasound or at necropsy, especially when only one kidney is affected and the other kidney has compensated.

Your vet will start with a history and physical exam, including questions about urine output, straining, feed, mineral program, water access, and whether the animal is male, castrated, pregnant, or recently ill. In some cattle, rectal palpation can help assess the bladder, urethra, or an enlarged kidney. If obstruction is suspected, your vet will also look for signs of pain, dehydration, abdominal distension, or uroperitoneum.

Bloodwork and urinalysis help show how much the urinary tract and kidneys are affected. Your vet may check kidney values, electrolytes, hydration status, and evidence of infection or blood loss. In ruminants with obstruction, azotemia and electrolyte changes may be present, although Merck notes these can be less dramatic than in monogastric species.

Ultrasound is one of the most useful tests. Published veterinary reviews describe ultrasonography as a helpful tool for diagnosing bovine urinary tract disorders, including hydronephrosis, urolithiasis, pyelonephritis, bladder rupture, and other urinary problems. Ultrasound can show dilation of the renal pelvis, thinning of kidney tissue, bladder size, free abdominal fluid, and sometimes the likely level of obstruction.

Depending on the case, your vet may also recommend catheterization attempts, abdominal fluid analysis, culture, or referral for advanced imaging or surgery. The goal is not only to confirm hydronephrosis, but to identify whether the blockage can be relieved and whether the kidney is still likely to recover.

Prevention focuses on preventing urinary obstruction and catching urinary disease early. Make sure cattle have steady access to clean water, especially in hot weather or when eating dry rations. Review the ration, forage, grain balance, and mineral program with your vet or nutritionist if urinary stones are a concern. Merck emphasizes that feed type, mineral supplementation, and water source all matter in ruminant urolithiasis.

Male cattle on high-concentrate diets may need especially close attention. Watch for straining, dribbling urine, tail switching, blood in the urine, or animals repeatedly standing to urinate without producing much. Early veterinary evaluation can sometimes prevent a lower urinary tract problem from progressing to bladder rupture or kidney damage.

Good herd health also matters. Prompt treatment of urinary tract infections, careful monitoring of pregnant cows with unusual abdominal findings, and post-illness follow-up in cattle with poor appetite or weight loss can help catch problems sooner. Hydronephrosis itself is not always preventable, but the earlier the underlying cause is found, the better the chance of protecting kidney function.