The term ‘wet tail’ can be used to describe a variety of conditions in hamsters, some more serious than others. True Wet Tail is a serious gastrointestinal infection which can be life-threatening. However, the term ‘wet tail’ is sometimes used more generally to describe any condition resulting in diarrhoea or wetness around the back end. 

True Wet Tail AKA Proliferative ileitis

Proliferative ileitis is a disease caused by the bacteria Lawsonia intracellularis which causes severe diarrhoea in hamsters. ‘Proliferative’ refers to proliferation or multiplication of cells. ‘Ileitis’ means inflammation of the ileum, a part of the small intestine. This name refers to the fact that this infection results in thickening and inflammation of the inner layer of the ileum due to proliferation of the mucosal cells. These changes prevent normal absorption of nutrients by the intestine; resulting in severe diarrhoea, dehydration, inappetence, weight loss and eventually death. The condition is most common in young hamsters around the time of weaning. A presumptive diagnosis of proliferative ileitis is often made based on observation of the characteristic clinical signs in a young hamster. 

Treatment can be attempted by administering a suitable antibiotic. Replacing fluid losses and providing supportive care including supplemental feeding; however, many affected hamsters will sadly succumb to the illness or require euthanasia due to the severity of the condition. 

It is possible for your hamster to be diagnosed with ‘wet tail’ due to the appearance of clinical signs similar to those seen with proliferative ileitis but which are being caused by a different condition. Some conditions causing diarrhoea or wetness around the back end are just as serious; however, others are minor and much more successfully treatable. 


Diarrhoea caused by something other than proliferative ileitis is an important alternative to consider. Something as simple as a sudden change in diet can upset the digestion, resulting in softer or wetter droppings. These can collect around the back end and tail, causing signs similar to those of true Wet Tail. Your vet may have an idea as to the likely cause by asking questions about the diet and any recent changes and by checking your hamster over to assess general health. Hamsters presenting with sudden onset diarrhoea due to simple reasons such as a sudden diet change will often still be bright and active in themselves and eating normally in contrast to hamsters with proliferative ileitis which are often unwell. 

Other causes of diarrhoea include bacterial, viral or parasitic intestinal infections other than Lawsonia intracellularis, side effects of certain antibiotics and as a secondary symptom of other diseases.

Urinary tract infections (UTIs)

UTIs can result in increased frequency of urination and urinary incontinence. As hamsters are often very secretive, the first noticeable sign is sometimes wetness around the bottom due to urine leakage. This can mimic the wetness around the back end seen with Wet Tail. Although concerning, many UTIs are simple and straightforward to treat especially if caught early. Your vet may suggest collection of a urine sample in order to assess for a urinary tract infection.

Vaginal discharge

Female hamsters produce a thick, creamy vaginal discharge during their normal reproductive cycle just after ovulation. This occurs once every four days and may be alarming. The discharge can be mistaken for pus or infection; however, this is completely normal and does not require any treatment. That said, a continuous vaginal discharge in an unwell female may be suggestive of infection and should be checked by a vet.

Polyuria and incontinence

The term polyuria means excessive urination and is often accompanied by polydipsia, meaning excessive thirst. These symptoms can be seen with a variety of conditions including kidney disease, diabetes and Cushing’s disease. Polyuria often results in leakage of urine and excessive wetting of the bedding. It may cause wetting around the back end and tail, mimicking signs associated with Wet Tail. Some of these conditions can result in weight loss and lethargy which are also signs related to Wet Tail. A veterinary examination, blood tests and urine tests can help to distinguish between these.

If you notice wetness around your hamster’s tail or back end it is really important to have them checked by your vet as soon as possible. Diagnosing the likely cause of the wetness helps to decide upon a suitable treatment plan and to determine the prognosis and likelihood of recovery. Not all causes of ‘wet tail’ are serious or life-threatening, but many can be if left untreated so having a check up sooner rather than later is the best way to ensure your hamster receives the care that they need.