Among the cases of ischemic colitis that occurred after left side colectomy, we treated 4 cases (2.1%) in which the congestion that caused ischemic colitis occurred because the arterial branch (SRA) was preserved and the IMV was resected near the root.
Among the surgeries for colon cancer performed at our hospital from January 2012 to December 2017, left side colon cancer surgery (transverse to sigmoid colon) was performed in 753 patients. These included 191 cases of left colectomy in which the SRA was preserved and the LCA or SA was resected; the IMV was dissected both at the inferior margin of the pancreas. PCC occurred in 4 of these patients (2.1%). PCC is defined as continuous edematous changes from the anastomosis site to the rectum, high-density adipose tissue around the mesocolon, and dilation of the vasa recti and arteries as seen on CT, as well as signs of ischemic colitis on colonoscopy.
All cases required long-term hospitalization for treatment, and in 1 case, the stenosis needed to be removed because it did not improve.
Ischemic colitis has been reported in 0.83% of cases when the IMA was treated at the root during resection of sigmoid colon or rectal cancer [3], and this condition is known to be associated with suture failure and prognosis [4, 6]. Most cases of postoperative ischemic colitis are associated with reduced arterial blood flow. However, in a previously reported case in which the blood vessels were treated similarly to our cases, ischemic colitis on the anal side of the anastomosis that occurred 1 year postoperatively may have been PCC [7].
The arterial blood flow to the left colon comes from the IMA, which generally branches into the LCA, SA, and SRA (Fig. 3a). In contrast, venous blood in the left colon returns to the descending colon, sigmoid colon, and rectum via the IMV. In left colon cancer, selecting which arteries to preserve and which to remove depends on the stage and location of the tumor. When the arterial branch is preserved, treating the IMV near the root may lead to imbalances in the venous return, which can create congestion (Fig. 3b). In the present cases, contrast enhancement from the IMA to the marginal artery and vasa recti indicated that ischemia due to arterial obstruction was unlikely (Fig. 2). We certainly confirmed that the marginal artery and the vein around the anastomosis were preserved. If there had been the damage of vessel or bleeding, the congestive ischemic colitis or even anastomotic leakage could have happened earlier.
Generally, occlusion of the IMV is idiopathic, due to deficiency of protein S or C, or accompanies coagulation abnormalities due to antiphospholipid antibody syndrome and presents with symptoms similar to PCC, such as mesenteric panniculitis of the colon or colitis [8,9,10]. Further, venous occlusion has been reported in a case of idiopathic mesenteric panniculitis [11]. In the present cases, because the IMV was resected at the inferior margin of the pancreas, we believe that venous return insufficiency caused the congestion and mesenteric panniculitis. The cause of imbalance was not clear, as mesenteric inflammation or microvascular mesenteric vein thrombosis caused venous occlusion and it may induce imbalance of blood flow.
PCC has the following 3 clinical features. First, congestion of venous return in the IMV region causes congestive colitis continuously from the anastomosis site to near the rectum. Venous return may be reduced starting from the anastomosis site when the residual sigmoid colon (return region) is long. The distance between the sacral promontory and the anastomotic site of cases 1 and 4 was longer than cases 2 and 3. Cases 1 and 4 needed more time to treatment (Table 1). In addition, continuous edematous changes from the anastomosis site to the rectum in CT are characteristic and make diagnosis easy.
Second, because it is venous congestion, the condition does not develop immediately after surgery; in the present cases, the condition took a median of 12.5 months (5–34 months) to appear (Table 1).
Third, all 4 cases experienced repeated watery stool from 1 week to 1 month before hospitalization. This was followed by symptoms such as abdominal pain and fever, after which diagnosis was made using CT.
Regarding treatment, resting the intestinal tract was the most effective. However, in case 4, the inflammation was severe and the stenosis on the anal side of the anastomosis did not improve even after ileostomy, making resection of the portion with colitis necessary. The inflammatory reactions did not improve even after administering antibiotics. While PEG1 has been reported to be effective for improving blood flow in postoperative ischemic colitis [12], it had no clear effects in cases 2, 3, and 4 (Table 2).
Trying to preserve as much of the IMV as possible could help prevent venous congestion, but preserving the main IMV trunk while resecting the branches is technically difficult. In transverse colon cancer, the area around the IMV is within the dissection range, which means this strategy could impact recurrence. When the IMV needs to be treated at the inferior margin of the pancreas for oncological reasons, the IMA to the SRA should not be preserved, the IMA should be dissected at the root, and anastomosis should be performed at a site with good blood flow. Alternatively, prevention may be possible by ensuring enough of the intestine on the anal side of the anastomosis is resected.
