Paraduodenal Pancreatitis
Introduction
Paraduodenal pancreatitis is a form of chronic pancreatitis that affects the pancreaticoduodenal groove (an anatomical area bounded by the duodenum, the head of the pancreas, and the common bile duct). Clinically and radiologically, this condition often resembles pancreatic ductal adenocarcinoma, duodenal or periampullary tumors, and cholangiocarcinoma. In recent years, the literature on paraduodenal pancreatitis has increased, but its differential diagnosis from oncological diseases remains challenging, sometimes leading to unnecessary surgical interventions. These interventions complicate patients' health and often worsen treatment prognosis. The exact prevalence of paraduodenal pancreatitis is unknown, but this pathology is diagnosed in 19.5–24.4% of cases following pancreaticoduodenal resections for chronic pancreatitis (1). This article aims to provide an overview of paraduodenal pancreatitis, focusing on its differential diagnosis from chronic pancreatitis and pancreatobiliary tumors.
Pathogenesis
This form of pancreatitis was first described in 1970 by Potet and Duclert (3), but its pathogenetic mechanisms have since been extensively studied. In 1991, Becker and Mischke identified two variants of the disease: true and segmental (3). In patients with true paraduodenal pancreatitis, the pancreaticoduodenal groove is affected without involvement of the pancreatic parenchyma or common bile duct. In the segmental variant, both the pancreaticoduodenal groove and pancreatic parenchyma are affected, leading to stenosis of the pancreatic duct and its proximal dilation.
The etiopathogenesis of paraduodenal pancreatitis is not yet clear. This is reflected in the various names used in the literature for this form of pancreatitis, such as cystic dystrophy of the heterotopic pancreas, paraduodenal wall cyst, periampullary duodenal wall cyst, pancreatic hamartoma of the duodenal wall, and myoadenomatosis. Each of these names reflects different histological types of damage.
Various pathogenetic mechanisms of this disease are being considered. According to one theory, the most important factor is impaired pancreatic juice flow through the accessory pancreatic duct (Santorini duct), which opens into the duodenum through the minor duodenal papilla located precisely in the pancreaticoduodenal groove. Increased pressure in the accessory pancreatic duct leads to reflux or backflow. This results in localized chronic inflammation of the pancreatic head involving the duodenum. Thickening of the duodenal wall occurs in the setting of chronic localized inflammation of the pancreatic head, leading to the formation of cystic structures. These can also form in the area of the pancreatic head. Duodenal stenosis often develops, while common bile duct stenosis occurs less frequently. Dysfunction of the accessory pancreatic duct may occur due to chronic alcohol abuse and anatomical or physiological variations in this area, which can make it more sensitive to alcohol (4). Heterotopia of the pancreas in the duodenal wall (chronic pancreatitis in an ectopic intraduodenal pancreas – cystic duodenal dystrophy) may also be significant (5). Leakage of digestive enzymes from the minor duodenal papilla into the pancreaticoduodenal groove, causing inflammation, could also play an important role. Increased viscosity of pancreatic juices, intraductal concretions, and calcifications, typical in patients who abuse alcohol, are also significant factors. These factors cause obstruction of the small ducts around the minor duodenal papilla, promoting the development of the disease. Therefore, there are several theories of pathogenesis, and each of them may have a rational basis.
Clinical Presentation
Most patients with paraduodenal pancreatitis are middle-aged men who abuse alcohol (7). Typical symptoms include upper abdominal pain after meals and impaired passage of contents from the stomach through the duodenum, leading to recurrent episodes of nausea and vomiting after meals. In advanced disease, patients complain of weight loss and intermittent episodes of jaundice (8). The duration of symptoms varies widely, from a few weeks to several years (9). Symptoms are usually more pronounced than in typical chronic pancreatitis. Laboratory tests are not very informative, although elevated levels of pancreatic and liver enzymes are typically observed. Patients may sometimes have falsely elevated levels of the cancer marker CA 19-9, presumably due to obstructive jaundice (10).
Examination
Endoscopic ultrasound is often considered one of the most informative radiological methods for diagnosing this disease. It easily identifies a hypoechoic area between the wall of the duodenum and the head of the pancreas. This method allows evaluation of duodenal wall thickening, narrowing of the intestinal lumen, pancreatic calcifications, pseudocysts, common bile duct strictures, and dilation of the pancreatic duct. The Santorini duct is either not identified or is found to be obliterated during the examination. Chronic pancreatitis is diagnosed or suspected much more frequently with endoscopic ultrasound than with magnetic resonance cholangiopancreatography (MRCP), and pancreatic tissue damage is assessed more accurately. When endoscopic ultrasound is performed, aspirate biopsy specimens alone are insufficient for comprehensive differential diagnosis; their findings must be correlated with radiological examination data and clinical findings.
Abdominal ultrasound examination reveals hypoechoic masses near the head of the pancreas. Thickening of the duodenal wall with proximal luminal stenosis, an irregular surface, and cystic changes may also be observed. Computed tomography shows changes often described as a sheet-like, hypodense mass in the pancreaticoduodenal groove, which increases the distance between the head of the pancreas and the duodenum. These changes persist during the arterial and venous phases and are characterized by late accumulation of contrast material. One of the main features identified on radiological examinations is thickening of the medial wall of the duodenum with cysts. These changes are particularly important for the differential diagnosis between paraduodenal pancreatitis and pancreatic adenocarcinoma, as they are not characteristic of the latter.
Differential Diagnosis
The differential diagnosis of true paraduodenal pancreatitis includes pathologies such as cholangiocarcinoma, duodenal and periampullary tumors, and acute pancreatitis with phlegmon near the pancreaticoduodenal groove. Endoscopic retrograde cholangiopancreatography (ERCP) or MRCP are the main tests used to differentiate this variant of pancreatitis from distal cholangiocarcinoma. In cases of paraduodenal pancreatitis, a long and smooth intrapancreatic portion of the common bile duct is observed, while cholangiocarcinoma is characterized by irregular and asymmetrical narrowing of the same duct. To differentiate true paraduodenal pancreatitis from acute pancreatitis with phlegmon, magnetic resonance imaging is the most suitable method. Phlegmons localized in the pancreaticoduodenal groove show a bright signal in T2 mode.
In the differential diagnosis of segmental paraduodenal pancreatitis, the main disease that must be differentiated is pancreatic carcinoma. This can be particularly challenging when pancreatic carcinoma has a significant fibrotic component on computed tomography, causing late accumulation of contrast material, a feature common to both carcinoma and paraduodenal pancreatitis. A key differentiating feature is the normal appearance of peripancreatic blood vessels in cases of pancreatitis. In contrast, pancreatic carcinoma that has spread to the peripancreatic tissues or duodenum usually encases and obstructs the peripancreatic vessels. ERCP or MRCP can also be used for the differential diagnosis of these pathologies. Segmental paraduodenal pancreatitis is characterized by a long, smooth, and narrowed intrapancreatic portion of the common bile duct. In patients with pancreatic head carcinoma, this portion of the duct is irregular and loses its usual shape, sometimes leading to complete obstruction.
Treatment
The treatment of paraduodenal pancreatitis is usually conservative. Prescribing analgesics along with complete alcohol abstinence, smoking cessation, and "pancreatic rest," i.e., a zero-fat diet, can be effective during the acute phase of the disease. Somatostatin analogs may have a positive effect because they inhibit exocrine pancreatic function, thereby affecting the pathogenesis of the disease. These drugs also have anti-inflammatory and cytoprotective effects. Minimally invasive treatment methods are also important, such as endoscopic drainage of the accessory pancreatic duct, stenting of the accessory or main pancreatic duct with plastic stents, drainage of cysts with pig-tail plastic stents, and stenting of the common bile duct. All these methods improve the patient's condition. This treatment can provide time to prepare for often necessary surgery – classic or pancreas-preserving pancreaticoduodenal resection.
Surgical treatment is indicated if there is chronic pain, weight loss, or severe pancreatic insufficiency. A prospective analysis of 62 cases published by Egorov and colleagues showed that early diagnosed paraduodenal pancreatitis is most effectively treated with duodenum-preserving pancreatic head resection. This observation suggests that the disease originates from the duodenum rather than the pancreas.
First Clinical Case
A 49-year-old man complained of nausea, vomiting, anorexia, and a feeling of pressure in the epigastrium lasting for 9 days. He lost 5 kg of body weight in a week. He denied alcohol consumption, autoimmune diseases, and pancreatic diseases among first-degree relatives. Upon objective evaluation, the patient had no fever, no signs of jaundice in the skin or sclera, and a negative abdominal rebound sign. Blood tests showed no signs of inflammation, anemia, electrolyte imbalance, or liver or kidney dysfunction. Blood lipase activity was elevated to 181 U/l.
Abdominal X-ray examination revealed no signs of free air under the diaphragm or bowel obstruction. Abdominal ultrasound showed a hypoechoic lesion between the head of the pancreas and the liver, with an unevenly thickened wall of up to 19.6 mm. The lesion measured 43 × 55 mm. The examiner suspected paraduodenal pancreatitis and suggested differentiating it from a pancreatic pseudocyst.
Due to suspected partial high intestinal obstruction, gastroduodenoscopy was performed. Large folds with signs of inflammatory infiltration were observed in the distal and proximal parts of the duodenal bulb, with some narrowing of the intestinal lumen, although the endoscope passed easily. Computed tomography of the abdominal organs was performed for the final diagnosis. It revealed infiltrative changes in the pancreatoduodenal region, thickening of the wall of the D2 segment of the duodenum with a cystic lesion measuring 28 × 18 mm, signs of luminal narrowing, and changes typical of paraduodenal pancreatitis. Following this examination, the clinical diagnosis was formulated as acute paraduodenal pancreatitis, subcompensated stenosis of the duodenum, and a cystic lesion in the wall of the duodenum.
The patient was hospitalized and prescribed a zero diet, infusion therapy, proton pump inhibitors per os, and intravenous antiemetics. As the patient's condition improved, tube feeding with Nutrison at 500 ml 3 times a day was initiated, along with additional digestive enzymes, continued oral proton pump inhibitors, and antiemetics. With further improvement in the patient's condition, disappearance of nausea and vomiting, and return of appetite, the patient was discharged on the 12th day of hospitalization to continue treatment on an outpatient basis.
Second Clinical Case
A 42-year-old man was brought to the Emergency Department by emergency medical workers due to nausea, vomiting, inability to eat normally, significant general weakness, and marked weight loss. These complaints had been ongoing for about 1 month. Upon objective examination, the patient was disoriented and lethargic but followed commands and answered questions. A brief episode of loss of consciousness and tonic seizures, which resolved spontaneously, were observed. The patient had an asthenic body composition, decreased subcutaneous fat, and a dry tongue. His body mass index was calculated as 16.37. In his medical history, the patient denied other diseases but admitted to alcohol consumption.
Blood tests showed a moderate increase in inflammatory markers, marked erythrocytosis due to dehydration, electrolyte imbalance (potassium concentration – 2.8 mmol/l), and elevated urea markers (urea concentration – 42.3 mmol/l; creatinine concentration – 350 μmol/l). A slight increase in blood lipase and liver enzyme activity was noted. Abdominal ultrasound revealed cholestasis, thick bile in the gallbladder, gastroparesis, a dilated pancreatic duct, and signs of chronic pancreatitis.
The patient was admitted to the Intensive Care Unit. Here, he was treated for exhaustion, electrolyte imbalance, and acute pancreatitis. He received 10 days of infusion therapy, intravenous vitamin B and proton pump inhibitors, anticoagulants, and enteral nutrition through a tube.
Gastroduodenoscopy revealed large folds in the distal and descending parts of the duodenal bulb that did not flatten when air was insufflated, with a narrowed lumen that was difficult to pass with the endoscope. Due to signs of intestinal stenosis related to extrapancreatic pathology, an enteral nutrition tube was inserted into the duodenum below the altered area during the procedure.
For an accurate diagnosis, abdominal computed tomography was performed. The pancreatic parenchyma enhanced uniformly, and the pancreatic duct was dilated to 7–8 mm. The pancreatic duct was narrowed in the head region, with a wide lateral duct visible. Tissues around the pancreatic head and duodenum were denser, with interspersed fluid and lymph nodes measuring up to 10 mm. The wall of the duodenum was thickened and edematous. The examination showed signs of paraduodenal pancreatitis, although tumor changes in the pancreatic head could not be ruled out. Repeat examination was recommended after the inflammatory markers decreased.
After the patient's condition improved, he was transferred to the Gastroenterology Department, where conservative treatment continued. With the return of appetite and a weight gain of 5 kg, the patient was discharged on the 15th day of hospitalization to continue treatment on an outpatient basis. He was advised to abstain from alcohol, avoid fatty foods, use proton pump inhibitors and digestive enzymes, and undergo monitoring and follow-up examinations on an outpatient basis.
Benediktas Kurlinkus, Prof. Algimantas Irnius
Vilnius University Hospital Santariskiu Clinic
Source: "Internistas", No. 1, 2016
