Background

The most appropriate surgical method for patients with a pancreatic head tumor and fat-replaced pancreatic body and tail has not been established [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. Essentially, total pancreatectomy (TP) is performed to excise the pancreatic head tumor, which results in subsequent loss of endocrine function and development of diabetes. Here, we report on a novel case in which adipose tissue was preserved during pancreaticoduodenectomy (PD) in a patient with a solid pseudopapillary neoplasm (SPN) and fat-replaced pancreatic body and tail. Preservation of the adipose tissue enabled retention of postoperative endocrine function and insulin secretion ability. Considering the novelty of our case, we also conducted a literature review of current evidence to gain insights into the procedural approaches in similar cases.

Case presentation

The medical examination of a 43-year-old man revealed calcification in the pancreatic head. He was referred to the Department of Gastroenterology for examination. No symptoms were evident, and his medical history was unremarkable. Contrast-enhanced computed tomography (CT) scans revealed a tumor (approximate size, 3 cm) with calcification in the pancreatic head. The pancreatic duct and parenchymal tissue were not observed on the caudal side of the portal vein. There were no liver metastases or enlargement of the surrounding lymph nodes. T1-weighted magnetic resonance imaging (MRI) scans showed low signal intensity, while T2-weighted MRI scans showed a reasonably high signal intensity in the pancreatic head. Furthermore, T2-weighted MRI scans indicated a high signal intensity in the pancreatic body and tail. Magnetic resonance cholangiopancreatography (MRCP) revealed that the pancreatic ducts of the pancreatic body and tail were completely disrupted (Fig. 1). Endoscopic ultrasonography (EUS) showed a low echoic mass with calcification, while contrast-enhanced harmonic EUS (CH-EUS) (Sonazoid, GE Healthcare, Oslo, Norway) revealed stark contrasts and hypovascularity in the tumor. EUS-guided fine-needle aspiration (EUS-FNA) was performed. Subsequently, the patient was diagnosed with a SPN.

Fig. 1
figure 1

Abdominal contrast-enhanced computed tomography and magnetic resonance imaging findings.a Abdominal contrast-enhanced computed tomography scan showing a mass measuring 30 mm in diameter with calcification, which projected forward in the pancreatic head without the body and tail. b T2-weighted magnetic resonance imaging scans showing a high signal intensity in the body and tail of the pancreas (arrowhead). c Magnetic resonance cholangiopancreatography image showing complete disruption of the pancreatic duct of the body and tail (arrow)

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Initially, we planned to perform a laparoscopic TP as intraoperative findings indicated that the tumor was present in the pancreatic head. Additionally, there was no pancreatic parenchyma in the pancreatic body, while that in the tail was completely replaced by adipose tissue. However, the shape of the pancreas could be identified. Based on these findings, a PD was performed on the left side of the portal vein (Fig. 2). As we found that the tumor had invaded the portal vein, we switched to open surgery. The pancreatic duct was not reconstructed, as the main pancreatic duct could not be identified at the cut surface. Therefore, only a modified Blumgart-style pancreaticojejunostomy was performed to cover the cut end. The surgery lasted for 425 min, and the volume of blood loss was 500 mL. Histopathological findings indicated that the pancreatic tissue was replaced by adipose tissue, and only Langerhans islets were observed (Fig. 3).

Fig. 2
figure 2

Surgical findings. a Caudal pancreatic tissue is replaced by adipose tissue. b Cut end of the pancreatic body replaced by adipose tissue

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Fig. 3
figure 3

Surgical specimens and histopathological findings. a Extracted specimen. b Examination of the resected specimen revealing a white nodular tumor extending to the body of the pancreas. The tumor contained calcified and hemorrhagic areas. c Histopathological findings (hematoxylin and eosin staining, × 20). d The pancreatic tissue is replaced by adipose tissue, and only a few Langerhans islets are observed (hematoxylin and eosin staining, × 40)

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The patient was discharged on postoperative day 12 without complications. He is being followed-up 1.5 years after the surgery. His fasting blood sugar and hemoglobin A1c (HbA1c) levels according to the National Glycohemoglobin Standardization Program (NGSP) reports were within the normal limits (HbA1c NGSP, preoperatively, 5.5%; 3 months postoperatively, 5.7%), indicating that endocrine function (insulin secretion ability) was preserved. He experienced diarrhea three times a day after the surgery; however, his nutritional status was maintained with oral administration of pancrelipase. His preoperative body weight and serum albumin levels were 87.6 kg and 4.6 g/dL, respectively, and by 3 months postoperatively, these were 81.4 kg and 4.6 g/dL, respectively.

Conclusions

Studies have reported that approximately 60% of patients with congenital aplasia in the body and tail of the pancreas develop diabetic complications [15]. Takahashi et al. [16] reported that atrophy and vitrification of the Langerhans islets were noted in autopsy cases of early-onset congenital aplasia in the body and tail of the pancreas, whereas an increased number of Langerhans islets and hypertrophy were found in some late-onset cases. Thus, diabetes mellitus in congenital aplasia of the body and tail of the pancreas is not caused by a single factor, but rather by the lack of Langerhans islets and several other acquired factors [16].

An electronic search in the Japan Medical Abstracts Society database (Ichushi web) using the phrases “agenesis of dorsal pancreas,” “aplasia of the pancreatic body and tail,” “dysplasia of the pancreatic body and tail,” and “hypoplasia of pancreatic body and tail” (excluding proceedings) yielded 91 case reports published since 1990. In 14 [1,2,3,4,5,6,7,8,9,10,11,12,13,14] of the 91 reports, the patients had undergone either TP or PD (Table 1). In TP cases, six patients developed diabetes before surgery and two patients developed diabetes after surgery. However, in PD cases (n = 6), patients did not develop diabetes at all. The loss of pancreatic tissue in the body and tail of the pancreas was noted in most patients who underwent TP; however, adipose tissue replacement of pancreatic tissue was not observed in any of these patients. Patients who underwent PD had no remnant pancreatic tissue, but did have adipose tissue, with the remaining Langerhans islets having replaced the lost pancreatic tissue.

Table 1 Reported cases of agenesis of body and tail of the pancreas undergoing total pancreatectomy or pancreaticoduodenectomy
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These results suggested that the Langerhans islets were retained in cases with adipose tissue replacement, which preserved endocrine function; thus, the patients did not develop diabetes. Therefore, we believed that performing PD with retention of fat-replaced pancreatic body and tail tissues in patients with pancreatic head tumors can preserve postoperative endocrine function. In addition, we performed a literature search for the reported procedures aimed at preserving adipose tissue in the pancreatic body and tail after PD. Tobita et al. [10] reported a patient with hypoplasia rather than agenesis of the dorsal pancreas. Furthermore, they found a main pancreatic duct requiring pancreaticojejunostomy. However, postoperative pancreatic juice leakage was observed. In our case, complete fat replacement of the pancreatic body and tail preserved the shape of the pancreas, but the main pancreatic duct could not be identified. Therefore, a modified Blumgart-style pancreaticojejunostomy was performed to prevent pancreatic juice leakage.

In addition, our literature review did not reveal any cases with anastomosis in the presence of fat-replaced pancreatic body and tail tissues, as performed in our case. Furthermore, postoperative pancreatic juice leakage was not observed in our case. These observations suggest that in cases where the remaining pancreatic tissue is completely replaced by adipose tissue and the main pancreatic duct is not identifiable, it may not be necessary to perform pancreaticojejunostomy.

In conclusion, in patients with the pancreatic head tumors, pancreaticoduodenectomy that preserves fat-replaced pancreatic body and tail tissues can preserve postoperative endocrine function.