Urinary Tract Infections (lower)


An inflammation of the bladder (cystitis), or urethra (urethritis). The lower urinary tract consists of the urethra and the bladder.

Clinical Signs

May observe any of the following:

  • An unusual frequency in urination.
  • Dampness of the fur from urine around perineum.
  • A firm and/or a distended bladder.
  • Blood or porphyrin in the urine.
  • Foul smelling or cloudy urine.

For additional information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Note: Any rat showing clinical signs of a urinary tract infection requires immediate attention by veterinarian.


Urinary tract infections can be caused by one or more of the following:

  • Bacteria
  • Fungal infections
  • Parasites (e.g., bladder threadworm)

The urinary tract, except for at the urethral orifice (the opening to outside the body), is normally a sterile environment free of pathogens. Infections to the urinary tract are caused by the presence of pathogenic microorganisms. Some of the organisms (in most cases bacteria) responsible are often found to be normal intestinal or fecal flora, such as E. coli and klebsiella, or mycoplasma found in the reproductive system.

Bacteria may gain entrance to the urethra and bladder through an ascending infection from outside the body. If the infection is left untreated it can move up to the ureters to involve the kidneys (pyelonephritis). Bacteria that is already present in the bloodstream, may also gain access to kidneys, ureters, and bladder through what is called a descending infection.

Mechanisms of the urinary tract help to oppose infections. The urine itself is bacteriostatic and bactericidal to many pathogens. The normal pH level of urine and the osmolality of urine help to inhibit bacterial growth. The unobstructed urine stream also helps to wash pathogens from the bladder and out through the urethra. The bladder wall, too, is a defense mechanism helping to prevent bacteria from entering the blood or lymph.
Any changes that occur in these defense mechanisms such as in a pH that is more alkaline can result in a negative effect of its antibacterial activity. Also any obstruction that may block the flow of urine, such as stones or congenital abnormalities, can cause the urine to “dam up”. This not only sets up an environment for bacteria to grow, but constitutes and emergency since partial or incomplete obstruction can result in the dilation of the kidneys (hydronephrosis), or if complete obstruction, renal failure and death.

Factors that can predispose the rat to developing urinary tract infections and increasing the chance of recurring or chronic infection are:

  • Any disorder that suppresses the immune system (e.g., diabetes).
  • Congenital (from birth) abnormalities of the urinary tract (e.g., diverticula of the bladder or a pouching that allows urine to remain stasis).
  • Blockages in the urinary tract such as stones (uroliths, calculi, crystals).
  • Inability to maintain hygiene.

For more information on blockages in the urinary tract due to stone formation see: Urolithiasis

For information regarding bladder threadworm see: Endoparasites.


Case History of Urinary Tract Infection (UTI)

  • Fig. 1: Urinary tract infection in 3 year old male rat (Shrek)


Obtain history.

Obtain urine sample for culture and sensitivity. This can be done either in the office or by having the owner obtain sample at home by lining a small carrier floor with plastic and placing rat in carrier upon waking. Once rat has voided aspirate urine with a syringe for testing.  3


For information pertaining to medications refer to the Rat Medication Guide.

The following are a list of some of the recommended antimicrobials based on urine culture:

Chronic or persistent infection may require long term antimicrobial therapy.

Nursing Care

  • Encourage fluid intake.
  • Refill drinking bottles daily with fresh water.
  • Continue course of antibiotic therapy as prescribed.
  • Cranberry juice may be given, however do not substitute this for fresh water, but rather give in addition too.
    It is believed that cranberry juice is helpful in lowering the pH of urine, but large quantities would have to be taken to do so. Rather, studies have shown that the chemical in cranberries and cranberry juice can inhibit bacteria like E. coli from sticking to the mucosal surface of the bladder and allow the bacteria to be flushed out with the passing of urine. See the following:

  • Offer yogurt, Lactobacillus capsules/granules, or Bene-bac , while taking antibiotics, to help maintain normal gut flora.
  • Observe and contact veterinarian if infection does not resolve or if worsens.
  • Outcome

    • Clinical signs resolved
    • Infection resolved / urine culture negative
    • No ova / parasites in urine
    • Rat is more comfortable


    • Treat any present infections or infestations as they arise.
    • Maintain a clean cage environment.
    • Provide clean fresh water and a healthy diet daily.
    • For elderly male rats or male rats with hind limb paralysis inspect and clean any waxy plugs that may form in the penis to prevent blockage of urine and bladder distention.
    • If rat experiences diarrhea, not only treat, but ensure the rat’s perineum is cleaned of any remaining excrement.


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