Torsion of a pedunculated accessory hepatic lobe: Cross-sectional imaging and histopathological correlation

Abstract

Accessory hepatic lobes represent uncommon birth defects that usually remain clinically silent and are discovered incidentally. Torsion of an accessory hepatic lobe is a rare complication causing abdominal discomfort difficult to discern from other etiologies of acute abdominal pain. Cross-sectional imaging is utilized to detect the process and establish a treatment plan. This case study presents a 57-year-old female with acute epigastric pain radiating to the right upper quadrant. Computed tomography and magnetic resonance imaging successfully identified an edematous, torsed accessory hepatic lobe. The patient underwent surgical resection of the torsed accessory lobe, and histopathologic analysis confirmed the process observed on imaging. Prior literature on imaging and histopathologic findings for accessory hepatic lobe torsion is limited. This report serves to describe key imaging features of this entity.

INTRODUCTION

Accessory hepatic lobes are rare congenital anomalies that result from abnormal development of the hepatic bud during embryogenesis. Typically, the liver is formed through an outpouching of the foregut endoderm that undergoes budding, asymmetric growth, and vascular remodeling.^[1] Variations in this process can result in accessory hepatic tissue connected to the native liver, typically through a stalk. Accessory hepatic lobes typically remain asymptomatic and are often discovered incidentally during imaging, surgery, or autopsy.

Pedunculated accessory hepatic lobes are at higher risk for complications including torsion, hemorrhage, or infarction. Torsion of an accessory hepatic lobe remains one of the rarest and most significant complications. Prior cases typically describe nonspecific abdominal pain that mimics other acute intra-abdominal pathology. Accessory hepatic lobes are infrequently observed, with reported incidences ranging from 0.7% at laparoscopy to 27.9% in cadaveric studies.^[2,3] Torsion of accessory hepatic lobes has only been reported sporadically in the literature.

Cross-sectional imaging plays a major role in identifying accessory hepatic lobes and detecting complications such as torsion and infarction. Furthermore, prior reports have focused on a discussion of surgical management; this report focuses primarily on the imaging and histopathological findings.

CASE REPORT

A 57-year-old female presented to the emergency department with a 3-day history of acute-onset, constant epigastric pain that radiated to the right upper quadrant. The patient was otherwise healthy, with no prior medical history or abdominal surgical history. The physical examination was significant only for epigastric and right upper quadrant tenderness. Review of systems identified accompanying nausea since the onset of abdominal pain. Initial labs revealed elevated (aspartate aminotransferase, 232 U/L and alanine aminotransferase, 166 U/L). Other indicators of liver function were within normal range, including alkaline phosphatase, total and direct bilirubin, and International Normalized Ratio. White blood cell count, serum hemoglobin, and platelet count were within normal limits.

The patient was then admitted to the medicine team. Computed tomography (CT) of the abdomen and pelvis with IV contrast revealed a 6.3 × 4.5 × 2.6 cm oval hypo-attenuating structure between the left hepatic lobe and pancreatic body that measured 44 Hounsfield units on portal venous phase [Figure 1a]. A prior abdominal CT with IV contrast performed 15 months earlier for blunt abdominal trauma showed a similar structure in the same region measuring 3.4 × 1.9 × 1.6 cm. However, enhancement matched adjacent liver parenchyma on the previous exam (115 Hounsfield units, [Figure 1b]). On both CT studies, the pancreas was visualized independently of the structure. Furthermore, the initial study demonstrated a vascular stalk that connected the structure to the liver itself, specifically to the caudate lobe. The lack of an identifiable stalk, increased size, and relative lack of enhancement of this structure on the current study raise suspicion for torsion of an accessory hepatic lobe.

Figure 1:

A 57-year-old female with an accessory hepatic lobe presented to the emergency department with epigastric and right upper quadrant pain. (a) Coronal abdominal computed tomography (CT) with IV contrast at presentation demonstrating an enlarged and hypoperfused accessory hepatic lobe (red arrows). (b) Prior coronal abdominal CT with IV contrast demonstrating a noninfarcted accessory hepatic lobe (white arrows).

An abdominal magnetic resonance imaging (MRI) was performed for further characterization. The aforementioned structure demonstrated decreased T1 signal and slightly increased T2 signal relative to the liver parenchyma [Figure 2], and a small amount of surrounding edema. There was no significant enhancement on post-contrast arterial phase images [Figure 3a]. On the portal venous phase, there was slight measurable enhancement, but significantly less than adjacent liver, suggesting hypoperfusion and/or infarction [Figure 3b].

Figure 2:

A 57-year-old female with an accessory hepatic lobe presented with abdominal pain. Axial T2 Fat-suppressed magnetic resonance imaging demonstrating relative T2 hyperintensity of the accessory hepatic lobe and surrounding edema (red arrows).

Figure 3:

A 57-year-old female with an accessory hepatic lobe presented with abdominal pain. (a) Axial T1 FS MRI in the arterial phase and in the (b) portal venous phase demonstrating relative hypoenhancement of the accessory hepatic lobe. Portal venous phase demonstrates internal hyperintensity (red arrow), suggestive of residual vascularization.

The patient was taken to the operating room for laparoscopic exploration, which confirmed torsion of an accessory hepatic lobe. The accessory hepatic lobe was resected [Figure 4]. A sample was taken to pathology and demonstrated normal liver parenchyma with the maintenance of central veins and portal tracts. These findings were accompanied by vascular congestion, edema, hemorrhage, and necrosis, compatible with torsion [Figure 5]. The patient was discharged on postoperative day 2 with resolution of the abdominal pain.

Figure 4:

A 57-year-old female with an accessory hepatic lobe presented with abdominal pain. Gross image of resected infarcted accessory lobe.

Figure 5:

A 57-year-old female with an accessory hepatic lobe presented with abdominal pain. Histopathological analysis of resected specimen. Sample showed normal liver parenchyma with central vein (blue arrow) and portal tract (white arrow). The hepatic parenchyma shows vascular congestion, edema, hemorrhage and necrosis, compatible with torsion. Hematoxylin and Eosin (H&E) at 4x magnification.

DISCUSSION

Cross-sectional imaging can play a significant role in the prompt identification of accessory hepatic lobes and their complications. On CT, noncomplicated accessory hepatic lobes demonstrate attenuation similar to that of the normal hepatic parenchyma and may demonstrate connection to the liver via a vascular pedicle. Small accessory hepatic lobes can be easily overlooked. CT findings of accessory hepatic lobe torsion can be explained by its pathophysiology. Torsion follows a predictable sequence: Vascular and lymphatic outflow obstruction leading to congestive edema, enlargement, venous hemorrhagic infarction, surrounding edema with arterial obstruction, concluding in ischemia, infarction, necrosis, gangrene, and/or surrounding inflammation.^[4] This is observed on imaging as enlargement of the affected lobe, hypoattenuation relative to the normal liver parenchyma, and decreased contrast enhancement, overall suggesting edema or infarction.^[5] Moreover, loss or twisting of the vascular pedicle may further suggest torsion. In this case, while the small accessory hepatic lobe was overlooked on the negative prior trauma CT, the presence of the comparison CT was able to highlight the interval change in size, attenuation, and vascularity.

MRI can further identify tissue changes within a torsed accessory lobe. T2-weighted imaging will generally demonstrate hyperintensity, reflecting increased tissue water content and edema. Conversely, contrast-enhanced T1-weighted imaging may demonstrate reduced enhancement due to a compromise in vascular supply.^[4,6] Although not observed in this case, contrast-enhanced imaging may reveal capsular enhancement associated with preserved arterial flow or neovascularization as a sequela of inflammation in cases of solid organ torsion.^[4] MRI findings from the literature are consistent with the present case and the pathophysiology of torsion.

While histopathological descriptions have been limited in the published literature and only described in veterinary reports, features of accessory lobe torsion include focal areas of necrosis along with portal vein congestion.^[7] In this case, pathology was notable for normal liver parenchyma with vascular congestion, hemorrhage, and edema. These findings were consistent with the present case, especially the finding of edema and ischemic injury; nevertheless, it should be noted that there was no observed radiologic evidence of hemorrhage. The preservation of normal hepatic architecture in this case suggests that the torsion was relatively acute, as a chronic onset or complete infarction would have demonstrated the loss of normal architecture and more widespread necrosis.

Previously published case reports on accessory hepatic lobe torsion have demonstrated a bimodal age distribution. Pediatric cases have been reported from in utero to adolescence, while adult cases have been reported in the fifth and sixth decades of life. For instance, a case of accessory hepatic lobe torsion has been reported in a 12-year-old female and another in a 54-year-old male.^[5,6] Despite this age distribution, there has been no clear demographic theme. Furthermore, most cases have been observed to occur spontaneously, without a clear predisposing factor.^[5] This case, involving a 57-year-old female with no prior surgical history or known predisposing condition, is concurrent with this pattern. The overall number of reported cases remains too small to make definitive epidemiologic conclusions.

Prompt diagnosis of accessory hepatic lobe torsion is significant as prolonged compromise may result in necrosis, infarction, or further complications such as sepsis, infection, or systemic inflammatory response syndrome. Consideration of this rare pathology and its radiologic features may facilitate earlier diagnosis and treatment. Findings such as interval enlargement, edema, and signs of vascular compromise should trigger suspicion for torsion of an accessory hepatic lobe in patients presenting with acute abdominal pain.

CONCLUSION

To the best of our knowledge, this is the first presentation of accessory hepatic lobe torsion focused on imaging and histopathological discussion. Accessory hepatic lobe torsion is a rare and difficult condition to diagnose. Early identification of imaging findings consistent with histopathologic evaluation (i.e., edema) can enable a more confident diagnosis.

Funding Statement

Financial support and sponsorship: Nil.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

Patient’s consent is not required as patient’s identity is not disclosed or compromised.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.