Indeterminant Lesions and the Role of EUS: A Cautionary Tale

Abstract

Purpose: The caudate lobe of the liver is divided inferiorly into a lateral caudate process and a medial papillary process. Below the porta hepatis, the papillary process may appear separate from the liver on transverse sectional images. A normal size or small papillary process may be mistaken for enlarged porta hepatis nodes on computed tomographic (CT) scans, whereas a large papillary process may mimic a pancreatic body mass. This can lead to unnecessary testing, further exposure to radiation, and possibly surgery. However, we present a case of the papillary process diagnosed by endoscopic ultrasound when all other imaging modalities failed. A 61-year-old woman was referred for abdominal pain. An initial ultrasound of the abdomen identified an echo poor mass near the pancreatic head. This prompted a CT of her abdomen confirming a 5.0 × 2.1 cm hypodense delayed enhancing lesion in the peri-pancreatic region of unknown etiology. The patient also had a PET CT scan which showed no increased FDG uptake in the soft tissue abnormality in the peripancreatic region but still no definitive etiology could be established. The patient was then referred for EUS, which yielded significantly different yet equally surprising results. An oblong 4.0 × 1.0 cm isoechoic lesion was seen immediately adjacent to the gastric wall and anterosuperior to the pancreatic body, it had a similar echo consistency as the adjacent liver and contained small scattered ductules. It was concluded that the “mass” was actually a papillary process of the liver, and this was confirmed by a follow-up MRI. Knowledge of the anatomy, sonographic pattern, and vascular relationships of the papillary process and surrounding structures enables the correct diagnosis in these two patients. This case demonstrates EUS as an invaluable approach for diagnostic and sampling of GI tract tumors and should always be considered as the surreptitious nature of smooth muscle tumors and other organs can lead diagnosticians astray. The sonographic appearance of the papillary process separated from the caudate lobe of the liver is an anatomic variant and is more commonly seen in in patients with chronic liver disease. In conclusion, the papillary process is a potential source of pitfalls in CT interpretation at and just below the porta hepatis. Given its anatomical placement and relationship to other organs, CT imaging and ultrasound can mistake it for a lymph node or pancreatic mass. This case demonstrates how every other imaging modality failed to delineate the source of this lesion but EUS was able to accurately diagnose it as a simple anatomic variant.