Diagnosing pancreatic steatosis in obese patients

Frequency of pancreatic steatosis in adults of general population is up to 35%. Causes of triglyceride accumulation in the pancreas include aging, obesity, type 2 diabetes mellitus, metabolic syndrome, hypertriglyceridemia (genetically determined or secondary one). Nomenclature by M. M. Smits is used for diagnosing, which sets out pancreatic steatosis, lipomatous pseudohypertrophy of the pancreas, fatty replacement of the pancreas, fatty infiltration of the pancreas, non-alcoholic fatty pancreatic disease, non-alcoholic pancreatic steatosis, non-alcoholic steatopancreatitis. 
Pancreatic steatosis usually does not have any clinical manifestations, as it is characterized by an asymptomatic course. It is diagnosed on the basis of results of imaging methods (ultrasound, computed or magnetic resonance imaging). According to the ultrasound, there are 3 degrees of pancreatic steatosis: 
 
Degree I — pancreatic echogenicity is equal to the echogenicity of adipose tissue in area of superior mesenteric artery. Pancreas is not enlarged, echogenicity is uniformly increased, contour is smooth, splenic vein, superior mesenteric artery and pancreatic duct are well-visualized; 
Degree II — increased echogenicity on the background of weak signal in the remote, dorsal part of the pancreas (reduced acoustic signal conductivity, attenuation of the ultrasonic signal behind the posterior surface of the pancreas), indistinct edges of splenic vein and pancreatic duct with almost non-visualized area of superior mesenteric artery; 
Degree III — reduction of ultrasound conductivity of the pancreas, undulating (convoluted), indistinct contours, splenic vein, area of superior mesenteric artery and pancreatic duct are not visualized. 
 
Main feature of the pancreas lesion in obesity is the absence of changes in biochemical indices or their minor changes. Exocrine and endocrine pancreatic insufficiency, hyperlipidemia may develop.

 Lipomatous pseudohypertrophy -an -extreme‖ variant of the accumulation of adipose tissue in the pancreas; total or local increase in pancreas; replacement of exocrine cells with adipocytes in the absence of an association with obesity.
 Fat replacementadipocyte replacement of dead acinar cells (for example, with viral infections, hemochromatosis, obstruction of pancreatic ducts), an irreversible process.
 Fatty infiltrationadipocyte infiltration due to obesity. According to the authors of the presented nomenclature, it is necessary to develop a differentiated approach to the diagnosis of conditions accompanied by the accumulation of triglycerides in secretory (acinous) cells, P-cells or in intrapancreatic adipose tissue. The lack of criteria for such a diagnosis limits the use of the existing classification [9].
-Steatosis‖ is a universal term that reflects the accumulation of intracellular fat in the organ parenchyma, and this process is considered as potentially reversible.
Along with it, the terms -lipomatosis‖, -fatty pancreatic disease‖ are also used, in the English language literature --fatty pancreas‖; these terms can be regarded as synonyms [10]. It was found that with a decrease in body weight, a decrease in pancreatic steatosis is observed in the case of the use of troglitazone, a combination of telmisartan and sitagliptin and some other drugs [1,7].

Diagnosis
With pancreatic steatosis, as a rule, there are no clinical manifestations, it is characterized by an asymptomatic course. Diagnosis is by imaging methods. For the diagnosis of pancreatic steatosis, general clinical, laboratory and instrumental examination methods can be used.
Complaints are uncharacteristic and non-specific. Pancreatalgia with pancreatic steatosisabdominal pain of low or moderate intensity, in the epigastric region or in the left hypochondrium, aggravated after eating or occurring 30-40 minutes after eating, sometimes radiating to the back. Dyspeptic symptoms in the form of vomiting, nausea, bloating are found in half of patients. Sometimes there is an increase in stool more than 2 times a day, its liquid consistency.
Exocrine insufficiency (the content of pancreatic elastase in the stool is less than 200 μg/g) is uncharacteristic for non-alcoholic fatty pancreatic disease.
Steatorrhea is rare, it occurs in patients with severe pancreatic steatosis or steatopancreatitis with exocrine insufficiency [10,13]. One of the methods of radiation diagnosis of pancreatic steatosis is ultrasound (ultrasound). The sensitivity of diagnosis of pancreatic steatosis using ultrasound varies from 37 to 94%, specificityfrom 48 to 100% [11]. Several approaches have been described to determine the degree of pancreatic steatosis. The hyperdiagnosis of pancreatic steatosis with ultrasound is most likely due to the fact that the density of the pancreas is compared with the density of the parenchyma of the kidney, liver and/or spleen, and not with the density of retroperitoneal fiber. Our studies and comparison of the results of computed tomography (CT) and ultrasound of the pancreas allowed us to offer the following method for diagnosing the degree of pancreatic steatosis [3].
Ultrasound diagnostic criteria for pancreatic steatosis:  norm: pancreatic density corresponds to the density of the cortical layer of the kidney;  mild: pancreatic density is higher than the echogenicity density of the cortical layer of the kidney, but lower than the density of retroperitoneal fiber;  moderate: pancreatic density corresponds to the density of retroperitoneal fiber;  severe: pancreatic density is higher than retroperitoneal fiber density.

Conclusion
For the early diagnosis of pancreatic steatosis, it is recommended to examine individuals with obesity, type 2 diabetes mellitus and signs of MS. The examination plan must include a biochemical blood test with the determination of the lipid profile, alanine aminotransferase, γ-glutamyl transpeptidase, lipase, glucose and abdominal ultrasound.