PD continues to be a difficult surgery even 100 years after its inception by Dr Walter Kausch and its modification by Dr. Allen Oldfather Whipple. With improvement of surgical techniques, though the mortality rate dropped, the morbidity still remained on higher side. Delayed gastric emptying, wound infection, post-pancreatectomy hemorrhage, postoperative pancreatic fistula (POPF), intra-abdominal abscess are amongst the common and serious complications following PD. Pancreatic anastomosis leak causing POPF still remains the leading cause of morbidity following PD even in specialized centers.[5, 6, 7] The main hurdle to manage POPF was lack of standardized and universally accepted definition until 2004 when 37 pancreatic surgeons from 15 countries formed International Study Group of Pancreatic Fistula (ISGPF) and purposed a definition for POPF. According to ISGPF, POPF was defined as measurable fluid output on or after postoperative day 3, with amylase content higher than three times the upper normal serum level. [8] It was revised in 2016 and divided POPF into biochemical fistula and clinically relevant fistula. [9]
The risk factors of POPF following PD can be various like etiologies for surgery, pancreatic parenchymal texture, duct diameter, surgical techniques, blood loss, high BMI. In regards to etiologies, PD done for pancreatic adenocarcinoma has a low risk for fistula formation in comparison to ampullary, duodenal, distal cholangiocarcinoma.[10,11,12,13] Risk of POPF increased many fold in patients with hard pancreas and small pancreatic duct diameter < (2-3) mm. [10,14,15]
Depending upon timing of its presentation, Veillette et al divided POPF into overt and occult fistula. Overt fistulas are defined by their evidence within first post-operative week and causes major morbidity and mortality. Occult fistulas are those which are not manifested in the initial post-operative period but subsequently resulted in intra-abdominal collection, abscess formation, hemorrhage and death. In their series, there were 13 occult fistulas. They also found that occult fistulas were responsible for repeated hospital admissions but there was no difference between them in relation to intervention, reoperation or mortality. But the occult fistulas in their study presented within 90 days of surgery. [16]
So, delayed presentation of POPF is a rare presentation which is rarer after PD and is only limited to individual case reports.[17] There are few case reports of delayed POPF after splenectomy.[18,19] Though the cause of delayed presentation of fistula is yet to be established, there are various plausible explanations. Pancreatic duct obstruction, recurrent pancreatitis, ischemia and fibrosis may lead to anastomotic disruption causing delayed POPF.[20] Pancreatojejunal anastomotic site stricture secondary to chemotherapy for pancreatic carcinoma may be another explanation.[21] Smoking which creates a thrombogenic environment along with its vasoconstrictive property may be another factor responsible for delayed POPF.[22] Small amount of initial leakage which often goes unnoticed may be aggravated by infection causing delayed fistula is another theory behind POPF. Gray zone between POPF and post-operative collections was described by Barreto et al. They proposed drains failing to drain properly due to blockage, displaced or misplaced drains and vascular factors may be responsible for delayed presentation of POPF.[23] In this case, though her immediate post-operative drain fluid amylase levels were normal ruling out an overt fistula, she presented with collections after receiving chemotherapy which may be the cause of delayed POPF by causing pancretojejunal anastomotic stricture.
Due to its rarity, the exact time duration of its presentation from index surgery is yet to be elucidated. Veillette et al in their series found all occult fistulas presented within 90 days of index surgery.[16] In a case report by Faraj et al, the duration was 7 years which is by far the longest interval reported in literature.[20] Ito et al reported a gap of 1 year and it was 8 months by Perez et al. In our case, patient presented to us after 6 months of index surgery. [24, 3]
Management of this unique condition may range from percutaneous drainage, endoscopic stenting of anastomotic stricture to redo of the anastomosis. [3, 20, 24] Patient was managed with antibiotics and percutaneous drainage in our case.
A delayed pancreatic fistula after PD is a rare complication and is limited to only individual case reports. This is the fourth case report on delayed POPF in literature to our best of knowledge. A little is known about its etiopathogenesis and few plausible explanations are available regarding the same without any concrete evidence. Few management options are available in the form of percutaneous drainage, stenting of anastomotic stricture and redoing the anastomosis. Though this study provides a different prospective to the existing literature about the delayed presentation of pancreatic fistula, a case series involving large number of patients is required to establish its etiopathogenesis and management.