The definition of steatorrhea is an increase in fat excretion in the stools. Steatorrhea is one of the clinical features of fat malabsorption and noted in many conditions such as exocrine pancreatic insufficiency (EPI), celiac disease, and tropical sprue. An increase in the fat content of stools results in the production of pale, large volume, malodorous, loose stools. Screening for steatorrhea may be carried out by examining stool samples for the presence of fat by Sudan III staining. However, quantitative fecal fat estimation is required to confirm the diagnosis.
Among the macronutrients, digestion and absorption of fat involve a complex mechanism. Fat absorption requires bile acids, digestive enzymes, and a normally functioning small intestinal mucosa. Dietary lipids, mostly as triacylglycerols, are initially emulsified by bile acids and then hydrolyzed by the pancreatic lipases and colipases into free fatty acids and monoglycerides. In the proximal small bowel, these hydrolyzed lipids form micelles by the action of bile acids. The micelles are then absorbed across the intestinal villi and transported as chylomicrons via the intestinal lymphatics. Therefore, any defects in the availability or function of bile acids, pancreatic digestive enzymes or absorptive villi will lead to steatorrhea.
The causes of steatorrhea are numerous and subclassify under three broad categories: (1) conditions leading to EPI, (2) bile acid deficiency states, and (3) diseases affecting the small intestine. Most notable disorders in each category are given below:
Other rare causes of steatorrhea include lipase inhibitors such as orlistat, Zollinger-Ellison syndrome (increased production of gastric acid inactivates the pH-sensitive pancreatic lipases), and graft-versus-host disease.
In the early stages, steatorrhea may be unrecognized by many patients due to minimal or nonspecific presenting symptoms. Therefore, the exact prevalence and incidence of steatorrhea are challenging to estimate and often go underreported. Also, the epidemiology of steatorrhea depends on the epidemiology of various underlying causes which is a topic of discussion below.
In adults, chronic pancreatitis is the most common cause of EPI. Chronic pancreatitis has an annual incidence of approximately 4 per 100000 persons and a prevalence of about 42 per 100000 individuals in the U.S. In children, CF accounts for most cases of EPI. CF is the most common lethal autosomal recessive condition affecting the White population. The approximate prevalence of CF is 1 in 3000 births. About 85% of CF patients have pancreatic insufficiency.
The prevalence of celiac disease is on the rise, and a recent study reported a global seroprevalence of 1.4%. Also, there are differences in the prevalence depending on geographical location. Reports of biopsy-proven celiac disease show lower prevalence rates in South America and Africa and higher rates in Europe and Oceania. For example, in Europe, Germany has a lower prevalence of celiac disease, and the highest prevalence was in Sweden and Finland. Celiac disease has a higher prevalence in certain high-risk groups such as type 1 diabetes mellitus, Down syndrome, Turner syndrome, IgA deficiency, William's syndrome, and in first-degree relatives of celiac disease.
Based on a study from the Netherlands, PBC had an incidence of 1.1 per 100000 (male to female ratio was 1 to 6.3) and the point prevalence was 13.2 per 100000 individuals in 2008. Another study from the U.S. reported an overall incidence of PBC as 2.7 per 100000 person-years and age and sex-adjusted prevalence of 40 per 100000 with a similar female predilection. PSC has a prevalence rate depending on the geographical location. A systematic review reported the incidence and prevalence rates of PSC ranging from 0 to 1.3 per 100000 people per year and 0 to 16 per 100000 people, respectively. As there is no consensus on the definition of SIBO, its exact prevalence is unknown.
Patients with steatorrhea present with bulky, pale, foul-smelling oily stools. These fatty stools tend to float in the toilet bowl and often challenging to flush as well. In the early stages, steatorrhea may be asymptomatic and go unnoticed. Patients also have other nonspecific manifestations of fat malabsorption such as chronic diarrhea, abdominal discomfort, bloating sensation, and weight loss. Children may present with growth failure and delayed puberty. In severe cases, loss of subcutaneous fat and muscle wasting may be evident. Manifestations of fat-soluble vitamin (A, D, E, and K) deficiencies can accompany fat malabsorption. Celiac patients can present with a variety of extraintestinal signs such as anemia, oral ulcers, and dermatitis herpetiformis rash. Abdominal pain is a predominant symptom in patients with chronic pancreatitis but also reported in other conditions such as SIBO, inflammatory bowel disease, and celiac disease. CF patients have sinopulmonary manifestations. Jaundice, fatigue, and pruritis are suggestive of cholestatic liver diseases such as PBC or PSC. Signs for end-stage liver disease such as splenomegaly, ascites can be noted in PBC or PSC.
List of conditions which present with steatorrhea:
List of conditions which present with chronic diarrhea which can be mistaken for steatorrhea:
Untreated steatorrhea leads to malnutrition and other complications such as fat-soluble vitamin deficiencies (A, D, E, and K). Identifying the cause of steatorrhea is vital for proper management and prevention of these complications.
The diagnosis of steatorrhea is usually delayed for months to years due to non-specific or minimal presenting symptoms during the early stages. A multidisciplinary team approach is often necessary for diagnosis, treatment, and follow-up. If steatorrhea is suspected clinically, the general physician and nurse practitioner should refer the patient to a gastroenterologist for consultation. As numerous conditions could contribute to steatorrhea, a systematic evaluation is required to expedite the diagnosis and to prevent further complications. The team should also include specialty-trained nurses and pharmacists. The involvement of a skilled dietician is indispensable for enhancing the nutritional status and limiting further malnutrition related adverse outcomes. [(Level V]
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