30 - SECTION 4 Disorders of the Pancreas

SECTION 4 Disorders of the Pancreas

Section 4 Disorders of the Pancreas Somashekar G. Krishna,

Darwin L. Conwell, Phil A. Hart

Approach to the Patient

with Pancreatic Disease ■ ■GENERAL CONSIDERATIONS Globally, pancreatic disorders, including acute and chronic pancreati­ tis, pancreatic cysts, and pancreatic cancer, are challenging to manage and associated with a high burden on health care resources. While the relationships between these diseases are multifaceted, there is ongoing scientific progress and a growing understanding in this field. Acute pancreatitis is one of the most common reasons for hospitalizations in gastroenterology, and there is increasing evidence of sequelae includ­ ing diabetes, exocrine pancreas insufficiency, and chronic pancreatitis. In elderly patients, acute pancreatitis may serve as an early symptom of pancreatic cancer. Chronic pancreatitis, an irreversible disease of the pancreas, associated with poor quality of life due to abdominal pain and associated exocrine insufficiency, is also an established risk factor for pancreatic cancer. Pancreatic cysts, mostly incidental, are increas­ ingly detected on cross-sectional abdominal imaging studies. Although only a small proportion of pancreatic cysts can progress to pancreatic cancer, the diagnostic uncertainty can introduce unwanted anxiety to patients and treating physicians. Meanwhile, with persistently high mortality rates, the incidence of pancreatic adenocarcinoma is increas­ ing and is the seventh leading cause of cancer-related death in the industrialized world and the third most common in the United States. PART 10 Disorders of the Gastrointestinal System As emphasized in Chap. 359, the etiologies and clinical manifesta­ tions of pancreatitis are quite varied. Although it is well-appreciated that acute pancreatitis is frequently secondary to biliary tract disease or alcohol abuse, it can also be caused by medications, genetic mutations, and trauma. In ~30% of patients with acute pancreatitis and 25–40% of patients with chronic pancreatitis, the etiology is initially unexplained. The global pooled incidence of acute pancreatitis is ~33.7 cases (95% confidence interval [CI], 23.3–48.8) with 1.16 deaths (95% CI, 0.85–1.6) per 100,000 person-years. The global pooled incidence of chronic pancreatitis is ~9.6 cases (95% CI, 7.9–11.8) with 0.09 attrib­ utable deaths (95% CI, 0.02–0.5) per 100,000 person-years. In the A B FIGURE 358-1  A. Side-branch intraductal papillary mucinous neoplasm (magnetic resonance imaging [MRI] with magnetic resonance cholangiopancreatography [MRCP]). T2-weighted MRCP image demonstrates a dominant, lobulated, hyperintense cystic structure (arrow) within the posterior body of the pancreas. The pancreatic duct upstream from the cyst is dilated and irregular. Endoscopic ultrasound and fine-needle aspiration of cyst fluid were consistent with a mucinous cyst. Surgical histopathology revealed an infiltrating moderately differentiated adenocarcinoma, 0.3 cm, arising in a background of an intraductal papillary mucinous neoplasm (IPMN). B. Mucinous cystic neoplasm (computed tomography [CT] scan). In the tail of the pancreas, there is a well-circumscribed hypodense cyst (arrow) without any nodular enhancing components. Endoscopic ultrasound and fine-needle aspiration of cyst fluid were suggestive of a mucinous cyst. Surgical histopathology revealed a mucinous cystic neoplasm (3.4 cm) with low-grade dysplasia. The stroma of the cyst demonstrated diffuse positivity for progesterone receptor and focal positivity for CD10 (ovarian stroma), confirming the diagnosis. C. Serous cystadenoma (MRI). A lobulated microcystic cyst (arrow) is observed in the tail of the pancreas. Neither a communication with the main pancreatic duct nor intracystic soft tissue enhancing nodular components were observed. However, the cyst continued to increase in size, and a distal pancreatectomy was performed. Histopathology revealed a serous microcystic adenoma. (Courtesy of Dr. Z.K. Shah, The Ohio State University Wexner Medical Center; with permission.)

United States, the number of patients admitted to the hospital with acute pancreatitis is increasing, with estimated rates of almost 300,000 annually, whereas the number of patients hospitalized for chronic pan­ creatitis is decreasing, with recent estimates of ~13,000 admissions per year. Chronic pancreatitis has an annual prevalence of 42–73 cases per 100,000 adults in the United States, although higher prevalence rates (0.04–5%) have been noted among adults at autopsy. Together, acute and chronic pancreatic disease costs an estimated $3 billion annually in health care expenditures. During the COVID-19 pandemic, it was noted that the infection was associated with elevated pancreas enzyme serum levels and presumed acute pancreatitis, though causal relation­ ships have not been definitively established. The diagnosis of acute pancreatitis is generally defined based on a combination of laboratory, imaging, and clinical symptoms. The diag­ nosis of chronic pancreatitis, especially in mild disease, is hampered by the relative inaccessibility of the pancreas to direct examination and the nonspecificity of the associated abdominal pain. Many patients with chronic pancreatitis do not have elevated blood amylase or lipase levels. Some patients with chronic pancreatitis develop signs and symptoms of exocrine pancreatic insufficiency (EPI), and thus, objective evidence for pancreatic disease can be demonstrated. However, there is a large reservoir of pancreatic exocrine function. Maldigestion of fat and protein becomes evident only when more than 90% of the pancreas is functionally damaged or obstructed. Noninvasive, indirect tests of pancreatic exocrine function (e.g., fecal elastase) are much more likely to give abnormal results in patients with obvious advanced pancreatic disease (i.e., pancreatic calcification, steatorrhea, or diabetes mellitus) than in patients with occult disease. Invasive, direct tests of pancreatic secretory function (e.g., secretin stimulation test) are the most sensitive and specific tests to detect early chronic pancreatic disease when imag­ ing is equivocal or normal. The increasing utilization of cross-sectional imaging modalities with their improved resolution has contributed to a high prevalence (2–5% with computed tomography [CT] scans, 20–30% with magnetic resonance imaging [MRI]) of incidentally detected pancreatic cysts. The most common cyst type encountered is an intraductal papillary mucinous neoplasm (IPMN), which is classified as a precancerous mucinous cyst. In the absence of high-risk features, radiographic surveillance is typically recommended (Fig. 358-1). Mucinous cystic neoplasms (MCNs) are relatively less common and occur almost exclu­ sively in women. Among the neoplastic cysts, serous cystadenomas have a negligible risk of progression to malignancy. Other infrequent neoplastic cysts include neuroendocrine tumors and solid pseudo­ papillary neoplasms. The most commonly encountered benign cyst is a pseudocyst, which can occur in patients with a history of acute C