LaPlace's law revisited: Cecal perforation as an unusual presentation of pancreatic carcinoma
© Slam et al. 2007
Received: 15 November 2006
Accepted: 02 February 2007
Published: 02 February 2007
Pancreatic cancer is often locally and distally aggressive, but initial presentation as cecal perforation is uncommon.
We describe a patient presenting with pneumoperitoneum, found at initial exploration to have a cecal perforation believed to be secondary to a large cecal adenoma, after palpation of the remainder of the colon revealed hard stool but no distal obstruction. Postoperatively, however, the patient progressed to large bowel obstruction and upon reexploration, a mass could now be delineated, encompassing the splenic flexure, splenic hilum, and distal pancreas. Histological evaluation determined this was locally invasive pancreatic adenocarcinoma, and therefore the true etiology of the original cecal perforation.
Any perforation localized to the cecum must be highly suspicious for a distal obstruction, as dictated by the law of LaPlace.
The law of LaPlace states: in a long pliable tube, the site of largest diameter requires the least pressure to distend. Hence, in a patient suffering a distal large bowel obstruction, in the setting of a competent ileocecal valve, the cecum is the most common site of perforation. Pancreatic carcinoma is often diagnosed late after aggressive local or distant invasion. However, pancreatic cancer initially presenting with cecal perforation secondary to large bowel obstruction from local colon invasion is distinctly uncommon. We report on the pitfall of missing this diagnosis.
After fluid resuscitation, he was brought to the operating room for exploration, where we encountered a minimal amount of fecal contamination and perforation of the cecum. A six centimeter non-obstructive mass and a hard mesenteric nodule were found in the cecum just distal to the site of perforation. The remainder of the colon was palpated and noted to be full of hard stool but otherwise without obvious abnormalities. We proceeded with copious irrigation of the peritoneal cavity and performed a right hemicolectomy with primary anastamosis without difficulty.
A closed loop bowel obstruction occurs when there is both distal and proximal occlusion to a segment of bowel, resulting in fluid accumulation without passage, strangulating the vascular supply to the affected segment. Typically, a patient with a closed loop obstruction will manifest tachycardia, leukocytosis, fever, or constant pain, but a lack of these symptoms does not exclude the diagnosis . Closed loop large bowel obstructions occur in the presence of a competent ileocecal valve, which inhibits the decompression of colonic fluid and gas into the small bowel .
Maintenance of competence at the ileocecal valve involves a complex interaction of anatomic and physiologic properties. The ileocecal valve is composed of two segments, an upper horizonal lip, and a longer and lower concave lip. The longitudinal muscle fibers of the bowel are continuous from the ileum to cecum, and the lips of the valve are formed by the mucous membrane and circular muscle fibers of the intestine . Autopsy studies have documented an additional impact of extrinsic fibrous attachments, the superior and inferior ileocecal ligaments, in maintenance of competence . Finally, manometric testing has demonstrated a tonic pressure at the ileocecal valve that variably responds to bowel distention, nerve stimulation, and pharmacologic manipulation . Barium studies have documented that between 70 and 90% of patients have an incompetent ileocecal valve, placing the approximately 10 to 30% of patients with a competent valve at risk for closed loop large bowel obstructions .
Laplace's law dictates that the intraluminal pressure needed to stretch the wall of a hollow tube is inversely proportional to its radius. The cecum is the largest diameter of the colon, and as such, requires the least amount of pressure to distend [7–9]. During a closed loop large bowel obstruction, the wall tension in the cecum increases, causing ischemia to the bowel wall. Microscopically, increasing wall tension can result in a longitudinal splitting of the serosa with a herniation of the mucosa through the diastasis of muscle. On gross inspection, the cecal perforation will typically be found on the anterior longitudinal axis, with sharp uninflammed margins .
It has been previously discussed that threshold for increased risk of cecal perforation is a diameter of twelve centimeters . Additional studies have suggested that the duration of dilation may be a more important risk factor for perforation than diameter of the colon [9, 11]. The intraluminal pressure required to result in colon perforation has been estimated through colonoscopic studies to be greater than 80 mmHg .
Large bowel obstructions distal to the cecum commonly present with proximal colonic dilation, placing the cecum at highest risk for perforation. Possible etiologies of large bowel obstructions include carcinoma, volvulus, fecal impaction, diverticulosis, inflammatory bowel disease, radiation enteritis, or pseudoobstruction . Rarely, reports of pancreatitis result in a closed loop colon obstruction with cecal perforation have been published . The presence of cecal perforation in a previously healthy individual must elicit a suspicion for distal colonic obstruction, especially secondary to carcinoma.
Pancreatic carcinomas lay latent for long periods of time before symptoms develop, determined by tumor location in the pancreas. Carcinomas of the head or uncinate process can cause bile duct, pancreatic duct, or duodenal obstruction. Patients may present with weight loss, painless jaundice, pancreatitis, nausea and vomiting from gastric outlet obstruction, steatorrhea, or back pain. Conversely, tumors of the neck, body, and tail of the pancreas usually do not result in jaundice or gastric outlet obstruction. Often, a mass at this location may only produce vague abdominal pain; new onset diabetes mellitus may be the only symptom of an occult carcinoma .
To our knowledge, pancreatic carcinoma initially presenting with local colon invasion, large bowel obstruction, and resultant cecal perforation has not been previously reported. Recent research has focused on the molecular basis for pancreatic carcinoma's aggressive local and systemic spread. Enhanced expression of the cell surface adhesion molecules such as ICAM and VCAM has been demonstrated in pancreatic cancer . Additionally, matrix metalloproteases (MMPs) are transmembrane proteins thought to have significant proteolytic activity on connective tissue in pancreatic carcinoma metastasis .
Comparison of colonic carcinoma and pancreatic carcinoma immunohistochemical staining patterns to the malignant tissues of this case adopted from reference 
Patients with colorectal cancer that suffer a proximal colon perforation secondary to their cancer have been found to have a lower local recurrence rate and higher disease free survival than those patients suffering a perforation at the tumor site via erosion through bowel wall . Pertaining to pancreatic cancer, only 11% of pancreatic carcinomas are confined to the tail of the pancreas, and over 50% of those pancreatic tail cancers present with stage four disease . Of patients undergoing treatment, the five-year patient survival of a stage four distal pancreatic cancer ranges from 1.6% with radiation alone, to 2.4–2.7% with chemoradiation therapy, to 11.9% with pancreatectomy only, to 19.3% with pancreatectomy plus chemotherapy . However, the survival benefit of an extended en block resection specifically of a locally advanced tail of pancreas cancer is unclear, though some studies have suggested a benefit, especially when combined with neoadjuvant chemoradation treatment .
Distal obstructions of the colon, in the presence of a competent ileocecal valve, may result in colonic perforation. The Law of Laplace dicates that the tension required to distend a hollow tube is lowest at the widest point. Clinically, this explains why the cecum is the most common site of perforation in a distal large bowel obstruction [7–9]. The surgeon must be vigilant at the time of initial exploration for cecal perforation and definitively rule out any distally obstructive cancers. An incidentally found non-obstructive lesion does not rule out a more distally located obstructive process.
Consent was obtained from the patient for publication of this report.
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