Urolithiasis

o bovis

Contributor(s):

Karin Mueller

Mike Reynolds

Synonym(s): Urethral obstruction, urinary calculus, water belly

Introduction

Cause: predisposing factors for uroliths (urinary calculi) to form include high concentrate/low forage diet and certain forages, as well as urease-producing bacteria and some antimicrobials. Obstructive urolithiasis is almost exclusively seen in the male, and in particular castrated males, because of a narrower and longer urethra compared to the female.
Signs: for urolithiasis without obstruction, small calculi may be seen on the preputial or vulval hair. Cystitis with its associated signs may also be observed. Obstructive urolithiasis results in anuria, stranguria, and / or dysuria, and commonly signs of colic. Where rupture of the urethra has occurred, urine commonly pools subcutaneously on the ventral abdomen.
Diagnosis: urine sediment examination. For obstructive urolithiasis, a combination of rectal examination, ultrasonography, blood biochemistry, and ruling out other causes of abdominal discomfort.
Treatment: for urolithiasis, urine acidification, lavage with Walpole’s solution and diuresis may be tried. Options for obstructive urolithiasis include smooth muscle relaxant, urethrotomy, urethrostomy or tube cystotomy. Salvage slaughter is not an option because of the uremia.
Prognosis: 35-95% reported depending on patient, approach and pathological changes present.

The most common scenario is that urinary calculi form in the bladder.
When such calculi are passed during urination, they may become lodged in the urethra leading to obstructive urolithiasis.
With a rarer occurrence and recognition, calculi may also form in the kidney (leading to nephrolithiasis), with the risk of lodgement in one or both ureters.

Dietary calcium to phosphorus imbalance or excessive dietary mineral intake. Common causes for these are:
- Diets high in concentrates (intake of >2.5% of bodyweight on dry matter basis for 2 months or longer), in particular in combination with low forage intake.
- Diets high in alfalfa (syn.lucerne), because of its high calcium content Calcium and phosphorus: overview.
Pastures with high levels of silica, oxalate or estrogens.
High levels of magnesium in calf milk replacer has also been reported.
Retinol (Vitamin A) deficiency may possibly play a role Vitamins: overview.
Less common are non-nutritional factors including urease-producing bacteria or certain antimicrobials (for example, sulphonamides).

Low salt content in the ration and restricted access to water supports precipitation of solutes Water requirements of cattle. In addition, the mineral composition of the drinking water may contribute to urolith formation.
Nidus formation, ie organic material forming the core of the calculus. Examples of such organic material are epithelial cells or necrotic tissue after local inflammation or infection Cystitis.
Castration results in narrowing of the urethra because of a lack of circulating testosterone.

Uroliths can form and reside in any part of the urinary tract. In addition to the more commonly recognized sites of urinary bladder and urethra, this also includes kidney (leading to nephrolithiasis) and ureter.
A common site for the urolith / calculus to lodge is the sigmoid flexure of the penis. However, it may also be located near the tip of the penis.
The common types of calculi seen in ruminants are:
- Phosphates (calcium, magnesium, or ammonium, and magnesium- (struvite calculi)) - beef animals on fattening ration .
- Silicate - extensive pasture .
- Calcium carbonate - clover pasture .
- Calcium oxalate - sugar beet tops.

Once obstruction has occurred, rupture of the urethra or urinary bladder is common after about 48 hours.
Hydronephrosis starts developing from about 48 hours after obstruction, leading to an ischemic and pressure nephropathy.

Incidence of 4-11% in abattoir studies reported.
Other male animals under the same nutritional management should be considered at risk after confirming the condition in an individual.