|Year : 2012 | Volume
| Issue : 3 | Page : 121-124
Caterpillar hump of right hepatic artery: incidence and surgical significance
Devi Jansirani1, N Mugunthan2, Vijisha Phalgunan2, S Shiva deep3
1 Assistant Professor of Anatomy, Sree Gokulam Medical College, & Research Foundation, Trivandrum, India
2 Assistant Professor of Anatomy, Mahatma Gandhi Medical College & Research Institute, Puducherry, India
3 Senior Resident,Department of Radiodiagnosis, Indira Gandhi Govt. General Hospital and Postgraduate Institute, Puducherry, India
|Date of Web Publication||23-Jan-2020|
Assistant Professor of Anatomy, Sree Gokulam Medical College & Research Foundation, Venjaramoodu PO., Trivandrum, Kerala - 695 607
Source of Support: None, Conflict of Interest: None
Background and aims: The right hepatic artery occasionally forms a sinuous tortuousity called as caterpillar hump or Moynihan’s hump, which occupies the major portion of Calot’s triangle. Due to this variation, inadvertent injury to right hepatic artery may occur during surgical procedures. The aim of the study is to find out the incidence of Caterpillar hump of right hepatic artery in cadavers and to correlate with surgical significance. Materials and methods: Sixty cadavers allotted for the purpose of teaching undergraduate students from the period of 2006 to 2011 were used for this study. Branches of coeliac trunk were traced and right hepatic artery was observed for the presence of caterpillar hump. Results: Caterpillar hump was noted in three out of 60 cadavers (5%). Out of three specimens with caterpillar hump, right hepatic artery passed posterior to common hepatic duct in two specimens and anterior to it in one specimen. The presence of dual loops of right hepatic artery was noted in two specimens and single loop was observed in one specimen. Conclusion: The presence of this variant course of right hepatic artery may lead to the formation of short cystic artery. Thereby, right hepatic artery can be mistaken for cystic artery and may be injured during surgical procedures. The knowledge of caterpillar hump of right hepatic artery is essential for the surgeons to avoid the risk of ischemic necrosis of right lobe of liver.
Keywords: caterpillar hump, Moynihan’s hump, tortuous right hepatic artery
|How to cite this article:|
Jansirani D, Mugunthan N, Phalgunan V, deep S S. Caterpillar hump of right hepatic artery: incidence and surgical significance. Natl J Clin Anat 2012;1:121-4
|How to cite this URL:|
Jansirani D, Mugunthan N, Phalgunan V, deep S S. Caterpillar hump of right hepatic artery: incidence and surgical significance. Natl J Clin Anat [serial online] 2012 [cited 2022 Aug 10];1:121-4. Available from: http://www.njca.info/text.asp?2012/1/3/121/298016
| Introduction|| |
Right hepatic artery is a branch of proper hepatic artery. It usually courses posterior to common hepatic duct. Before entering into porta hepatis, it gives off cystic artery which enters into Calot’s triangle to supply the gall bladder.
Numerous variations in origin and branching pattern of right hepatic artery have been reported. But, tortuous right hepatic artery, running with upward and downward course producing hump is quite rare. This sinuosity of the right hepatic artery is called as Caterpillar hump or Moynihan’s hump. The variant course of right hepatic artery may lead to vascular injuries during surgical procedures like cholecystectomy, liver transplantation, etc.
The aim of this study is to find out the incidence of caterpillar hump of right hepatic artery in cadavers and to correlate with the possible surgical significance.
| Material and Methods|| |
A total of 60 cadavers irrespective of age and sex from three Medical colleges namely Madurai Medical College, Madras Medical College and Mahatma Gandhi Medical College and Research Institute, Puducherry were used for this study from the period of2006 to 2011. Abdomen was dissected following Cunningham’s practical manual and the branches of coeliac trunk were traced and right hepatic artery was observed for the presence of caterpillar hump.
| Observations|| |
Out of 60 cadavers, caterpillar hump of right hepatic artery was observed in three cadavers (5%).
In this specimen [Figure 1], proper hepatic artery divided into a tortuous right and left hepatic artery. Right hepatic artery coursed posterior to common hepatic duct forming a typical sinusoid course. Initially it had a proximal loop facing upwards and after entering into Calot’s triangle it had a distal loop with a bold convexity facing downward and to right, closer to cystic duct. From the distal loop of caterpillar hump, a short cystic artery arose and divided into superficial and deep branches to supply the gall bladder.
|Figure 1: Shows caterpillar hump right hepatic artery (RHA) with dual loops, coursing posterior to common hepatic duct (removed, shown in dotted line) and middle hepatic artery (red asterisk). Blue asterisk shows the short cystic artery from distal loop of RHA. Left hepatic artery (LHA) was retracted with forceps.|
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In this specimen [Figure 2], proper hepatic artery divided into right and left hepatic artery. The right hepatic artery coursed anterior to common hepatic duct. It presented a twist pointing upwards as proximal loop and swung towards right to form the distal loop. From the point of maximum convexity of distal loop of Moynihan’s caterpillar hump, the cystic artery arose and supplied gall bladder.
|Figure 2: Shows right hepatic artery (RHA) twisted to form two loops of caterpillar hump, swinging anterior to common hepatic duct. Blue asterisk shows cystic artery arising from the distal loop of right hepatic artery.|
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In this specimen [Figure 3], right hepatic artery arose from proper hepatic artery and coursed posterior to common hepatic duct. Inside the Calot’s triangle, it produced caterpillar hump with only one loop with convexity facing downwards and to the right, from which the cystic artery arose.
|Figure 3: Shows right hepatic artery (RHA) arising from proper hepatic artery (PHA) and passing posterior to common hepatic duct (CHD) to form single loop of caterpillar hump inside the Calot’s triangle. Blue asterisk shows cystic artery from the point of maximum convexity of caterpillar hump of RHA.|
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PHA-proper hepatic artery; CYS-D -cystic duct; GB - Gall bladder; CBD -Common bile duct; PV- Portal vein;CHA - Common hepatic artery; GDA - Gastro duodenal artery; RGA - Right gastric artery; CHD - Common hepatic duct; LHA - Left hepatic artery.
| Discussion|| |
According to Benson and Page, the incidence of caterpillar hump of right hepatic artery was 5-15%. In the study reported by Carol et al, its incidence varies from 6-16%. Out of 35 specimens, Johnston and Anson found only one specimen with caterpillar hump of right hepatic artery (2.86%). Bergamaschi et al in their postmortem study, found caterpillar hump of right hepatic artery as one of the third content of Calot’s triangle in 12.9 % of the specimens. Out of 60 specimens, Prithi et al found caterpillar hump of right hepatic artery in one specimen (1.6%). In the present study, the incidence of caterpillar hump was 5% which was in concordance with the result of previous studies.
As compared with splenic artery, the tortuousity of the hepatic artery is relatively rare; yet in some cases, the hepatic artery makes a full circle twist inside and outside the Calot’s triangle comparable with the loops formed by splenic artery in aged individual. In Calot’s triangle such loops may pass ventral or dorsal to the common hepatic duct. In the present study, the tortuous right hepatic artery passed dorsal to common hepatic duct in two specimens and ventral to it in one specimen.
The characteristic sinuosity of the right hepatic artery is extremely vulnerable to injury during cholecystectomy as the cystic artery may arise from the proximal or from the distal portion of the loop. If cystic artery arises from the proximal loop, it has to cross the right hepatic artery. In the present study, out of three specimens showing caterpillar hump, proximal loop and distal loop were present in two specimens and single loop was present in one specimen. In both cases with two loops, cystic artery arose from the distal loop of caterpillar hump.
There is scarce information available in the literature regarding the etiology of caterpillar hump formation. Taylor et al reported a possible explanation that the hepatic artery is more liable to become elongated and tortuous during cirrhosis. This may be due to the underlying architectural distortion associated with corkscrewing of intrahepatic branches of hepatic artery.
Due to this variant course, the right hepatic artery was in close proximity to cystic duct and gall bladder. This results in the formation of a short cystic artery. So, the right hepatic artery may be mistaken as cystic artery and inadvertently ligated during surgical procedures like cholecystectomy and liver transplantation,,,,.
Since the cystic artery arising from caterpillar hump is typically short, it may get easily avulsed from the hepatic artery, if excessive traction is applied to the gallbladder. The presence of a caterpillar hump should be suspected when an unusually large cystic artery is viewed through the laparoscope.
This redundancy combined with small arterial twigs to gall bladder rather than a single cystic artery renders right hepatic artery susceptible to injury. Thus right hepatic artery may be damaged when these small arteries are to be controlled for bleeding.
Some of the safety rules to be followed during cholecystectomy procedure may help the surgeons to avoid the inadvertent injury of the caterpillar hump right hepatic artery. They are: freeing the infundibulum (pediculization) first in order to widen the Calot’s triangle, tracing the cystic artery until it reaches the gall bladder wall before clipping it, separate ligation of cystic artery and cystic duct to avoid arterio-biliary fistula, always keeping the dissection plane close to the gall bladder wall and meticulous dissection without bleeding for better visualization.
Pseudoaneurysm of the hepatic artery is considered as one of the post-operative complications following laparoscopic cholecystectomy. The main concern to prevent this complication is to avoid the iatrogenic injury with the awareness of anatomical variations in hepatic artery including the caterpillar hump of right hepatic artery. In case of bleeding, the surgeon should not hesitate to convert a laparoscopic cholecystectomy into open cholecystectomy .
| Conclusion|| |
To conclude, the incidence of presence of caterpillar hump or Moynihan’s hump of right hepatic artery in this study was 5% (3 out of 60). Out of three specimens with caterpillar hump, right hepatic artery passed posterior to common hepatic duct in two specimens and anterior to it in one specimen. The presence of dual loops of right hepatic artery was noted in two specimens and single loop was observed in one specimen.
In the presence of this variation, usually the right hepatic artery runs close to the cystic duct occupying major area of the Calot’s triangle. Since the right hepatic artery is closer to cystic duct, the cystic artery may be short. The knowledge of this anatomical variation is mandatory for the surgeons to avoid the inadvertent ligation of right hepatic artery instead of cystic artery, thereby preventing vascular injuries and the fatal ischemic necrosis of the right lobe of the liver.
The authors acknowledge the following faculty members for their constant support to conduct this study.
- Dr. Christilda Felicia Jebakani, Professor and former Director, Institute of Anatomy, Madras Medical College, Chennai.
- Dr. V. Rajaram, Professor and Director in-charge, Institute of Anatomy, Madurai Medical College, Madurai.
- Dr. Sudha Rao, Professor and Head, Department of Anatomy, Mahatma Gandhi Medical College and Research Institute, Puducherry.
- Dr.J.Anbalagan, Professor, Department of Anatomy, Mahatma Gandhi Medical College and Research Institute, Puducherry.
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[Figure 1], [Figure 2], [Figure 3]