Pancreatic abscess, a rare complication of peptic ulcer disease

Clinical History

84-year-old male suffering from appetite loss, malaise, intermittent low-grade fever since a few weeks, sent to emergency department by family physician under clinical suspicion of upper digestive tumour. Physically found dehydrated, with epigastric tenderness but no peritonism.
Emergency laboratory tests within normal limits, apart from elevated C-reactive protein (30 mg/L).

Imaging Findings

CT (Fig. 1) showed a vast abscess with some internal gas occupying the pancreatic region, with residual enhancing pancreatic parenchyma at body and tail, which abutted the contracted antropyloric tract with circumferential mural thickening with oedematous submucosa and hyperenhancing mucosa suggesting severe gastritis. Additionally, focused multiplanar reconstructions identified a focal communication between the pancreatic abscess and the inflamed pyloric-duodenal tract: the origin of fistulisation corresponded to endoscopic finding (Fig. 2) of a large ulcer at the posterior aspect of the proximal duodenum, of unclear peptic or neoplastic nature.
At laparotomy, surgical findings confirmed difficult dissection of lesser sac, presence of a large, foetid purulent and necrotic collection occupying the pancreatic region, fixed to the stomach and deformed pylorus. Abscess toilette and partial gastric resection with Billroth-II gastrojejunostomy were performed, as documented by early postoperative CT (Fig. 3) which excluded complications.
Histology confirmed severe transmural ulcerated peptic gastro-duodenitis with perivisceral inflammation, without malignant changes.

Discussion

Despite effective medications and anti-Helicobacter pylori (HP) eradication, peptic ulcers (PUs) of the distal stomach, pylorus and duodenal bulb remain a major health problem worldwide with a prevalence ranging from 1.5% in the USA to 10% in low-income countries, and still represent one of the main indications for emergency surgery. Whereas in industrialized regions HP-related PUs are declining, an increasing proportion of ulcers results from use of nonsteroidal anti-inflammatory drugs including cardioprotective aspirin, plus cofactors such as smoking and alcohol consumption. As a result, PUs are increasingly encountered in advanced age, predominantly in males, and may be complicated by haemorrhage, perforation, gastric outlet obstruction and fistulisation in descending order of frequency [1, 2].
Whereas PUs remain the first cause of intraperitoneal perforation, posterior ulcers may occasionally penetrate into the retroperitoneum. Clinical presentation may be either hyperacute (epigastric pain, severe tenderness, fever) or insidious (abdominal or back pain, malaise weight loss). Leukocytosis, elevated acute phase reactants, serum amylase, lipase and hepatic transaminases are generally present. Surgical treatment via laparotomic approach is generally required, and often involves extensive dissection, gastric resection or duodenectomy [3-6].
When faced with more or less fluid-attenuation collections with peripheral enhancement, the diagnosis of retroperitoneal abscess is relatively straightforward: the vast majority result from superinfection of post-necrotic collections after severe acute pancreatitis, or exceptionally from haematogenous spread [7, 8]. The presence of air-attenuation components may result from gas-forming bacteria or from visceral fistulisation. Conversely, the underlying PU is easily overlooked at CT, since the non-distended stomach and duodenum are difficult to assess, particularly when peristaltic movements or retained content are present. Albeit endoscopy is the pivotal technique for PU diagnosis, it is invasive and often unfeasible in emergency: thus most patients with abdominal pain and unknown peptic disease presenting to emergency department undergo CT as the initial examination. As in this case, careful multiplanar CT interpretation may allow suggesting the correct diagnosis: antral, pyloric and proximal duodenal mural thickening with hyperenhancing mucosa and submucosal oedema reflect severe gastro-duodenitis and warrant endoscopy. The presence of perigastric or periduodenal fat inflammatory changes represent helpful ancillary finding. Albeit superficial ulcers are poorly or not identified, larger and/ or deeper PUs may be recognized as mucosal interruption with focal outpouching (corresponding to the ulcer “crater”) extending beyond the visceral wall. In elderly people, the key differential diagnosis is represented by ulcerated gastroduodenal tumours, which are heralded by soft-tissue attenuation mural thickening [9-12].

Differential Diagnosis List

Final Diagnosis

Pancreatic abscess from perforated peptic ulcer of proximal duodenum.

URL:	https://eurorad.org/case/14507
DOI:	10.1594/EURORAD/CASE.14507
ISSN:	1563-4086