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Introduction
Groove pancreatitis (GP), also described as paraduodenal pancreatitis, is a rare form of segmental chronic pancreatitis characterized by fibrotic scarring of the pancreatoduodenal (PD) groove, an anatomical area bound by the pancreatic head, duodenum, and common biliary duct (CBD) [1]. There are two forms of GP: pure GP occurring solely within the pancreaticoduodenal groove and segmental GP also affecting the pancreatic head [2, 3]. Its pathophysiology remains unclear, but it is likely to be multifactorial with a common pathway being the obstruction of the minor papilla [4]. Imagiological findings include fibrotic changes of the pancreatic groove and the presence of duodenal wall cysts as well as the thickening of the duodenal wall, pancreatic head enlargement, CBD, and Wirsung duct stricture. Given the clinical and radiological resemblance to pancreatic cancer, the diagnosis is challenging and frequently requires surgical intervention [5, 6]. We report two cases of GP as well as a review of the literature. Both our patients were male with a history of alcohol consumption and had a similar clinical and imag-ing presentation. However, they were managed differently with one of them requiring pancreatoduodenectomy.
Case Report 1
A 52-year-old male patient, with a history of hypertension and dyslipidemia, active smoking habits (35 pack units/year), and alcohol consumption over 100 g of alcohol daily, presented to the emergency department with right quadrant abdominal pain for over 5 months, with irradiation to the back associated with vomiting and weight loss (6% of the total body weight in 1 year). On examination, tender right hypochondrium palpation was noted. No signs of peritoneal reaction, ascites, or organomegaly were observed. Liver function tests, bilirubin, and amylase were within the normal ranges. He was referred to an outpatient consultation for follow-up.
The patient was reevaluated 5 months later, and because of his persistent abdominal pain and vomiting, an upper endoscopy was performed and revealed a bulging of the duodenal bulb with irregular mucosa. Duodenal biopsies were negative for neoplastic cells. Abdominal CT scan revealed diffuse parietal thickening of the second duodenal portion and diffuse densification of the surrounding tissues with preserved pancreatic structure and no Wirsung duct dilation (shown in Fig. 1). Serum carcinogen antigen 19.9 (CA 19.9) and IgG4 were normal. An abdominal magnetic resonance imaging (MRI) revealed heterogeneity in the pancreatic-duodenal recess, thickening of the second duodenal portion with a central cystic image (8 mm), and maintained pancreatic morphology and dimension (shown in Fig. 1). An endoscopic ultrasonography (EUS) showed hyperechoic foci and parenchymal lobularity, aspects of chronic pancreatitis, without pancreatic head nodular lesions or Wirsung duct dilation. Despite alcohol withdrawal, tobacco reduction, and pain medication, intense abdominal pain persisted with a great impact on the patient’s quality of life. An abdominal CT was performed 14 months after the initial presentation, showing the same findings as before. The case was discussed at an oncology multidisciplinary meeting, and after discussion with the patient, he was submitted to a cephalic pancreaticoduodenectomy with complete remission of the abdominal pain. The pathology result was compatible with GP (shown in Fig. 2). At 5 years of follow-up, the patient is asymptomatic.
Fig. 1. Abdominal CT of case 1 showing a crescentic mass-like structure in the groove region (*) which causes duodenal stenosis (a) with a normal pancreas structure without Wirsung duct dilation (b) MRCP showing a smooth tapering of CBD (arrow) (c) and in a T2-weighted image (d) a cyst in the groove region. CT, computed tomography; MRCP, magnetic resonance cholangiopancreatography; CBD, common biliary duct.
Case Report 2
A 63-year-old male with active smoking habits (60 pack units/year) and alcohol consumption (25 g alcohol per day) presented with a 1-month history of unintentional weight loss (31% of previous weight, BMI 15 kg/m2) associated with postprandial vomiting and abdominal pain for 2 weeks. On examination, epigastrium and right hypochondrium tenderness on palpation were noted. He had no jaundice, palpable masses, or lymph nodes. Liver function tests, pancreatic enzymes, IgG4, and CA 19.9 were normal. Abdominal CT scan (shown in Fig. 3a) showed increased volume of the pancreatic head with small calcifications and a CBD of 8-mm upstream from the intrapancreatic portion. Upper endoscopy revealed extrinsic duodenal bulb compression (shown in Fig. 3b). EUS showed a heterogeneous pancreatic head parenchyma with hyperechoic foci with shadowing, but without Wirsung duct dilatation and duodenal wall thickening (25 mm). There was no evidence of nodular lesions (shown in Fig. 3c). The patient was maintained with naso-jejunal feeding during 15 days with weight gain and pain relief.
Fig. 3. a Abdominal computed tomography of case 2 showing enlargement of pancreas head with foci of cystic degeneration (*) and CBD dilation (8 mm) (arrow). b Upper endoscopy of case 2 showing duodenal stenosis (bulb represented) by extrinsic compression. c Endoscopic ultrasound of case 2 showing hypoechoic bandlike thickening of the pancreaticoduodenal groove, as well as thickening of the adjacent duodenum and a hypoechoic heterogeneous pancreatic head. CDB, common biliary duct.
The case was discussed at a multidisciplinary meeting, and it was decided to maintain the patient under active surveillance with conservative treatment. The patient stopped alcohol and tobacco consumption. Three months after discharge, he gained 18 kg and had no abdominal pain or vomiting. The MRI showed thickening and cystic changes in the duodenal wall and delayed enhancement in the PD groove, with a nondilated CBD. At 5 years of follow-up, he was asymptomatic and had normal laboratory tests.
Discussion/Conclusion
GP - Pathophysiology
GP is a type of segmental chronic pancreatitis, first described in 1973 by Becker [2] with the German word Rinnenpankreatitis and translated into GP in 1982 by Stolte et al. [7]. The true incidence and its underlying etiology remain uncertain, but the central mechanism seems to be an anatomical or functional outflow obstruction of the minor papilla [1, 8-10]. The vast majority of patients have significant alcohol consumption, indicating that alcohol plays a major role in promoting pancreatic juice viscosity and exacerbating the inflammatory process [11]. Various factors contribute to outflow obstruction: pancreatic heterotopia in the duodenal wall with localized inflammation and duct dilation; Brunner gland hyperplasia, which can occur from chronic alcohol stimulation or from increased levels of cholecystokinin; or gastrin and pancreas divisum with subsequent increased pressure in the minor papilla [9, 12, 13].
Clinical Symptoms
GP manifests most commonly in men in their fourth to fifth decade of life with a history of chronic alcoholism, as occurred in our 2 cases [9]. The typical clinical symptoms are severe upper abdominal pain, nausea, recurrent postprandial vomiting, and weight loss [14]. Rarely, some patients can present with duodenal stenosis. Jaundice is rare and is often more suggestive of an underlying malignancy [10].
Diagnosis
The differential diagnosis includes pancreatic adeno-carcinoma, periampullary cancers, pancreatic groove neuroendocrine tumor, autoimmune pancreatitis, and acute pancreatitis [3, 5]. Although in some patients, there are significant clinical and imaging features of GP, there is often overlap with other infiltrative processes involving the pancreatic groove, namely pancreatic cancer. Table 1 summarizes the clinical, laboratorial, and imagiological differences between GP and cancer.
Table 1. Clinical, laboratory, and imaging features for distinguishing GP and pancreatic cancer arising in the groove region
Laboratory values and biochemical markers are often nonspecific. While liver function tests and bilirubin are generally within the normal range, alkaline phosphatase levels can be elevated even in the absence of biliary obstruction. Amylase and lipase may be slightly increased [4, 11]. Tumor marker’s carcinoembryonic antigen and CA19.9 levels are generally normal. However, obstructive jaundice, if present, may cause an elevated level of CA 19.9, not related to an underlying malignancy [15]. IgG4 levels should be measured since autoimmune pancreatitis may mimic GP [16].
Imaging Features
Contrast-enhanced CT and MRI are the primary imaging modalities used when GP is suspected. The classic imaging features on CT scan consist of an illdefined crescentic soft tissue mass seen in the PD groove with the pure form of GP. In its segmental form, there is a mass-like enlargement of the whole pancreatic head that can be indistinguishable from pancreatic cancer. The duodenal wall is involved in 92% of patients with luminal narrowing due to wall thickening. Smalls cysts are seen within the duodenal wall or in the PD groove itself, in 81% and 75% of cases, respectively [17]. This common finding in GP contrasts with its rarity in pancreatic adenocarcinoma. CBD may be narrowed with a smooth, tapered, and regular stenosis [4, 11].The peripancreatic vessels are typically maintained, in contrast with the typical encasement in cases of adenocarcinoma. MRI shows a “sheet”-like mass of tissue, which is hypointense on T1-weighted images and variable in T2-weighted images, according to the time of disease onset [5]. Duodenal wall thickening is also seen, and T2-hyperintense cysts can be found in both the duodenal wall and PD groove [4, 9]. A study conducted by Kalb et al. [18] indicates that during focal thickening (>3 mm), abnormal increased enhancement of the second portion of the duodenum and cystic changes in the region of the pancreatic accessory duct are all present, the diagnostic accuracy is 87.2%, and a diagnosis of cancer can be excluded with a negative predictive value of 92.9%. Upper endoscopy typically shows mucosa edema, erosion, polypoid appearance of the descending duodenal part, and luminal stenosis [9]. EUS is considered by some authors the preferred imaging method as it provides high-resolution images of the head of the pancreas and PD groove, and it allows to obtain tissue sampling [5]. In GP, EUS can detect a hypoechoic band-like thickening of the PD groove and adjacent duodenum with intramural cysts, smooth stenosis of CBD and, in the segmental forms, a heterogeneous hypoechoic pancreatic head mass. Nonetheless, EUS is not able to differentiate inflammation and malignant infiltration in several cases [4, 11, 12].
Histopathology
Pathologic analysis of the pancreatic resection specimen is the only definitive way of diagnosing GP. Gross examination shows active and chronic inflammation of the PD groove, adjacent duodenal wall, and pancreatic head, as well as extensive scarring. Cystic spaces (0.2-2 cm) can be identified within the duodenal muscularis propria and submucosa and/or PD groove [9, 19].
The histological aspect of GP is characterized by thickening of the duodenal wall, inflammation of the Brunner gland and smooth muscle hyperplasia. Sometimes, heterotopic pancreatic tissue in the duodenal wall is identified, but this finding is not universal. Spindled stromal cells are the most common finding after fine needle aspiration (FNA). However, endoscopy-guided FNA biopsy presents great variability depending on the area sampled and the presence of cytological features associated with reactive cellular atypia resulting from pancreatitis may mimic neoplasia [4]. To our knowledge, there are no studies comparing EUS-guided FNA versus FNB, specifically in GP. However, recently, Wong et al. [20] compared the diagnostic performance of EUS-guided tissue acquisition by EUS-guided FNA versus EUS-guided FNB for solid pancreatic mass, and they found that the diagnostic yield of solid pancreatic mass was higher in FNB than in FNA (94.6 vs. 89.6%).
Treatment
Currently, there are no treatment guidelines on GP. When an accurate diagnosis of GP is possible, patients may be treated conservatively. Conservative therapy includes analgesia, alcohol and tobacco cessation, and parenteral nutrition when enteral nutrition is contraindicated, the patient does not meet the daily energy needs for more than 10 days, or in case of gastric or intestinal outlet obstruction [12]. There are also some reports of cases using somatostatin analogs, but the results appear to be temporary [21]. Endoscopic treatment may involve pseudocyst drainage, pancreatobiliary stent placement, or duodenal dilation. When cancer cannot be safely excluded, surgery is advised. Surgical treatment encompasses pancreatoduodenectomy, the most common procedure, and digestive or biliary bypass operations.
A recent systematic review evaluated clinical outcomes in GP after treatment [14]. The treatment was conservative in 29%, and half of the patients had complete symptom relief. Endoscopic and surgical treatment occurred in 12% and 59% of cases, respectively. Although surgery resulted in complete symptom relief in most of the patients (79%), it is associated with a high rate of complications (20%) [14]. Furthermore, in a large case series from Arvanitakis M et al., medical treatment associated with endoscopic approach (pancreatic ductal drainage, stricture dilation, and cyst drainage) allowed completed clinical success in 80% of the cases [22]. Thus, a stepwise approach, starting with conservative treatment, is recommended, unless malignancy cannot be ruled out.
In conclusion, we present the 2 cases of patients with classic risk factors, including alcohol and tobacco abuse, and symptoms of GP. Furthermore, they have similar clinical, laboratory, and imaging findings, namely, normal CA 19.9, parietal thickening of the descending part of the duodenum, and cystic changes without pancreatic duct dilation or vascular encasement. Thus, chronic abdominal pain and vomiting in a patient with history of alcohol abuse and no significant laboratory findings can point out to a chronic pancreatitis like GP. The treatment should be individualized, but a surgical approach may be necessary, as indicated in the first case.
