Testing for Abdominal Enlargement in Cats

What does abdominal enlargement mean?

Abdominal enlargement is a general term that means a cat’s belly is larger or fuller than usual and bulges beyond the normal outline of the body. Abdominal distension is another term that has a similar meaning, but often refers to more severe cases of abdominal enlargement.

What are some causes of abdominal enlargement?

Abdominal enlargement may develop for many reasons depending on the age and gender of the cat. It can be a simple problem and even a normal condition in some pets. However, abdominal enlargement can also indicate serious underlying disease.

Simple Causes of Abdominal Enlargement

Intestinal parasites (worms). Large numbers of worms in the intestine can cause distension of the abdomen, giving the pet a pot-bellied appearance. This is condition is typically seen in kittens and treated with de-worming medication.

Obesity. Weight gain usually occurs when a cat eats too much, does not exercise enough, or both. Obesity leads to accumulation of fat in the abdomen and may result in abdominal enlargement. In cats, obesity can also be a sign of hormonal imbalance.

Pregnancy. Pregnant female cats show abdominal enlargement by mid- to late pregnancy. Unspayed cats that run free outdoors often get pregnant without their owners knowing, and unsuspecting owners may be surprised by the abdominal enlargement that follows. The easiest way to prevent pregnancy is to spay your cat, preferably at a young age. If your cat is not spayed, try to be aware of when your cat is in heat (ready to mate), and you will be prepared for possible abdominal enlargement due to pregnancy.

Abdominal Enlargement Associated With Illness

Organ enlargement. An increase in the size of one or more abdominal organs can cause the abdomen to appear distended. Organ enlargement is often a sign of underlying illness such as infectious disease, inflammation, tumors (cancerous or non-cancerous) and other conditions. Unspayed female cats can have enlargement of the uterus. It can be filled with fluid, mucous or pus, a life-threatening condition called pyometra. This condition requires emergency spay surgery.

Free fluid in the abdomen. The accumulation of fluid in the abdomen is always a cause for concern. The free fluid can be urine or blood, or it can be an effusion (fluid that escapes from body tissues and collects in the abdomen).

• Free urine in the abdomen indicates the bladder, ureters, or urethra have been damaged and urine is leaking; this usually follows trauma such as being hit by a car. Some cats, especially males, can form a urethral obstruction due to several causes, which leads to bladder distension and possible rupture.
• Free blood in the abdomen is associated with trauma, surgery, bleeding disorders, and some types of tumors.
• Effusions can develop for many reasons, such as liver disease, heart disease, low blood proteins, abdominal tumors, and inflammation of the abdominal lining. Effusions should always be investigated to find the underlying cause.

Tumor/cancer. Tumors and cancers affecting abdominal organs often result in abdominal enlargement.

Heart disease. Heart failure can result in enlargement of the liver and cause free fluid to build up in the abdomen, resulting in abdominal enlargement.

Feline infectious peritonitis (FIP) is a potentially fatal viral disease that can cause build-up of free fluid in the abdomen and/or the chest. When the fluid accumulates in the abdomen, the cat shows abdominal distension.

Rare in cats but worth noting:

• Hypothyroidism. This disease develops when the thyroid gland fails to produce enough thyroid hormone. Hypothyroid animals become sluggish and gain weight, even if they eat less and exercise. Fat builds up around the abdominal organs and over time leads to a bulging abdomen.
• Cushing’s disease. This is a disorder of the adrenal glands, also known as hyperadrenocorticism. Affected animals typically have abdominal enlargement due to enlargement of the liver, accumulation of fat in the abdomen, and a weakened body wall.

How is the cause of abdominal enlargement determined?

Your veterinarian will perform a complete history and physical examination. Your cat’s history of illness refers to details about how long your cat has had abdominal enlargement, how quickly it appeared, and any event that might have occurred before you noticed the change.

Physical examination involves checking over the entire cat, listening to the heart and lungs with a stethoscope, and palpating the abdomen (gently squeezing or prodding the abdomen with the fingertips to identify abnormalities). A complete examination may detect heart disease, organ enlargement, an abdominal mass, the presence of free fluid or intestinal gas, and other abnormalities that could explain the abdominal enlargement.

Further testing is usually required, and your veterinarian may recommend screening tests that provide information about the overall health of the pet. The most common screening tests are complete blood count (CBC), serum biochemistry profile, and urinalysis.

What might the screening tests indicate?

1. Complete blood count (CBC). This simple blood test provides information about the different cell types in blood, including red blood cells, which carry oxygen to the tissues; white blood cells, which fight infection and respond to inflammation; and platelets, which help the blood to clot. The CBC provides details about the number, size, and shape of the various cell types, and identifies the presence of abnormal cells. See handout "Complete Blood Count" for further information.

The CBC might reveal a decrease in the number of red blood cells in the blood, a condition called anemia. More severe anemia in a cat with a distended abdomen could signal bleeding into the abdomen due to trauma or an abdominal tumor. An increase in the number of white blood cells could indicate infectious disease, inflammation associated with a tumor, or accumulation of fluid in the abdomen.

2. Serum biochemistry profile. This test involves a chemical analysis of serum - the pale-yellow, liquid part of blood that remains after the cells and clotting factors have been removed. There are many substances in serum, including proteins, enzymes, fats, sugars, hormones, and electrolytes. Measuring the levels of the various substances in the blood provides information about the health of the body’s organs and tissues such as the liver, kidney, and pancreas, and helps to detect diabetes. See handout "Serum Biochemistry" for further information.

In cats with abdominal distension, abnormal biochemistry results may indicate which organ is affected and what the problem might be. Some examples are:

• Abnormally high levels of the liver-related enzymes alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma glutamyltransferase (GGT) could signal underlying liver disease.
• Very low levels of albumin (a blood protein) can cause fluid to accumulate in the abdomen and could explain abdominal distension. Albumin can be lost through the gastrointestinal tract due to inflammatory bowel disease or other severe intestinal illnesses, or through the urine with kidney disease.
• High levels of serum globulin (proteins produced by the immune system) could signal underlying inflammation, infection, or cancer; the viral infection FIP is an example of a disease that may cause increased levels of serum globulins.
• Very low blood sugar levels could be a sign of insulinoma (a cancer of the pancreas).

3. Urinalysis analyzes the chemical and physical properties of urine. A urinalysis is important in any sick pet and is necessary for the proper interpretation of the serum biochemistry profile, especially in a pet that has kidney disease or diabetes. See handout "Urinalysis" for further information.

What other tests can be done to investigate abdominal enlargement?

Depending on the results of the history, physical examination, and screening tests, additional testing could include:

• Specific blood tests. Specialized blood tests may be used if a particular disease or illness is suspected. Tests include:
  • Serum bile acid tests to detect liver disease
  • Antibody tests for specific infectious diseases
• Imaging studies. Radiographs (X-rays) and ultrasound are often recommended to assess internal organs and to look for possible abdominal masses. More sophisticated techniques such as magnetic resonance imaging (MRI) and computed tomography (CT scan) may also be recommended if they are available.
• Testing for heart disease. This testing could involve chest X-rays, a heart ultrasound (echocardiogram), electrocardiogram (EKG), or specific blood tests such as ProBNP.
• Biopsy. Biopsies may be taken if a tumor or free fluid in the abdomen is suspected.
• Free fluid. Free fluid in the abdomen is easily collected by abdominocentesis, which involves passing a sterile needle through the body wall into the abdomen. A sterile syringe is attached, and gentle suction is used to remove a small amount of fluid. The collected fluid is sent to a referral laboratory to be analyzed by a veterinary pathologist.
• Abdominal mass or enlarged organ. Masses or enlarged organs may be sampled by fine needle aspiration or tissue biopsy. Both types of samples can be collected through the skin with the help of an ultrasound or collected directly during surgical exploration of the abdomen. Collected tissue samples are sent to a referral laboratory for analysis by a veterinary pathologist.

What is the prognosis for abnormal abdominal enlargement?

The prognosis varies depending on the cause. If the underlying cause is a condition that can be managed, then the prognosis is good. Traditionally, FIP was a fatal disease. However, newer treatments have emerged and there is now hope for cats suffering from this condition. Some conditions, such pyometra or urethral obstruction, may be corrected with emergency surgery. Other causes, such as cancer, heart disease, or liver disease, may be managed for a period of time, but have a poor long-term prognosis.