Fecal examination

Even when the results of a fecal examination (flotation and direct smear) are negative, empirical deworming is often appropriate.

Acholic (i.e. gray, clay-colored) stools can be seen with exocrine pancreatic insufficiency and nonsuppurative cholangitis-cholangiohepatitis. The latter can produce intermittent acholic stools, and it may be appropriate to have the owner bring in five consecutive days of stools in a cat with other signs of this disease, such as chronic elevation of liver enzyme activities, increased appetite, or hepatomegaly.

Blood pressure measurement is an underused diagnostic tool, but it is becoming a standard of care in veterinary medicine. Systemic hypertension is a systolic blood pressure ≥ 160 mm Hg. Diseases associated with hypertension in cats include chronic or acute renal failure, hyperthyroidism, diabetes mellitus, and neurologic disease. Intracranial disease increases systemic blood pressure as a compensatory mechanism.

Increased age increases the risk for hypertension, particularly because renal insufficiency and hyperthyroidism are more common in elderly cats. All cats more than 10 years old should undergo routine screening for hypertension.¹¹ Using 10 years of age as a guideline for beginning the routine monitoring of blood pressure can be supported by studies of hypertensive cats. In a study of 69 cats with hypertensive retinopathy, 64 (92.7%) were older than 10 years,¹² and in another study of 58 cats with hypertension, 84% were older than 10.¹³

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The results of initial diagnostic tests may indicate that other diagnostic tests such as radiography, pancreatic immunoreactivity tests, cobalamin and folate measurement, and fecal alpha₁-protease inhibitor measurement are needed. Ultrasonography, cytology, histology, and endoscopy or laparoscopy may also be warranted.

Radiography

Thoracic and abdominal radiography is often needed after routine laboratory testing and helps to identify masses, organomegaly, fluid accumulation, or calcified areas (e.g. uroliths, nephroliths, intestinal cancers, choleliths). Choleliths may be occasionally seen with cholangitis-cholangiohepatitis complex and chronic pancreatitis. An enlarged sternal lymph node may be seen with abdominal inflammatory or neoplastic disease, since this lymph node drains portions of the abdomen. Poor abdominal radiographic detail can result from fluid accumulation, carcinomatosis, or a lack of body fat.

Pancreatic immunoreactivity tests

Measuring fasting trypsin-like immunoreactivity (TLI) and pancreatic lipase immunoreactivity (PLI) is often indicated to diagnose GI disease and has become fairly routine in some practices.* Exocrine pancreatic insufficiency is diagnosed by identifying decreased TLI concentrations. Although diarrhea usually occurs in cats with exocrine pancreatic insufficiency, it may not always be observed in cats that eliminate outdoors; weight loss may be the only reported clinical sign.

PLI is the preferred blood test for diagnosing feline pancreatitis. Compared with TLI, it is more sensitive and specific,¹⁴ and serum PLI concentrations stay elevated for much longer.¹⁵ PLI is also more accurate than ultrasonography.¹⁴ If the PLI concentration is normal, moderate to severe pancreatitis can be confidently ruled out, and an elevated PLI will accurately diagnose feline pancreatitis about 90% of the time.¹⁴

Cobalamin and folate measurement

Measuring the serum cobalamin (vitamin₁₂) concentration is recommended in cats with chronic GI disease.* Because adequate serum cobalamin concentrations depend on normal pancreatic protease activity and normal absorption by binding to specific receptors in the ileum, cobalamin deficiencies may be found with chronic disorders of the distal small intestine and with exocrine pancreatic insufficiency.¹⁶ Because cobalamin is required for metabolism, cobalamin deficiency may contribute to the clinical signs of GI disease and lead to suboptimal response to treatment of the primary disease.

Increased serum folate concentrations* can be a sign of small intestinal bacterial overgrowth because bacteria in the small intestine produce folic acid, which is then absorbed into the bloodstream.