Effects of portasystemic shunting on visceral and portal blood flow in the dog

Late effects of portasystemic shunting on visceral and portal vein blood flows were evaluated in mongrel dogs with radioactive microspheres. Sham operation (n = 5) produced no significant long-term changes in visceral blood flow. In contrast, there was a significant increase in small bowel perfusion 3 wk after selective and nonselective portasystemic shunting: end-to-side (n = 7), side-to-side (n = 7), H-graft mesocaval (n = 5), and distal splenorenal (n = 11). Variable increases in pancreatic blood flow were noted in all shunt groups. Portal venous blood flow was significantly elevated in all dogs with total shunts and was substantially increased in animals with H-grafts. Compared with baseline levels, perfusion of organs left in continuity with the portal vein after splenorenal shunting was significantly increased. Blood flow from the small bowel was primarily responsible for the magnitude of the change in portal venous flow. The reduction in hepatic perfusion by portal venous blood appears to trigger these compensatory responses. A humoral mediator best explains the phenomena observed.

Ischemic diseases of the large intestine

The blood flow within the walls of the digestive tract must be sufficient to maintain its structural and functional integrity. All episodes of vascular insufficiency cause ischemic damage to the organ and carry the threat of diffuse or focal necrosis. Certain forms of ischemic colitis or proctitis arise from episodes of reduced peripheric or splanchnic blood flow; indeed, those which do not culminate in necrosis of the colonic wall are more frequently caused by hemodynamic disorders than by vascular occlusions. The crisis is often mitigated by the development of collateral circulation; this is, however, of rather poor quality so patients become very vulnerable to subsequent slight changes in cardiac output. Necrotic, gangrenous ischemic colitis arises from a combination of occlusive damage to the arteries and general hemodynamic disturbances. The vascular insufficiency may be slight or severe, temporary or long-lasting, localized or diffuse. In addition, the attack occurs in a septic medium in the presence of abundant microbial flora which may be highly pathologic. Thus infection complicates and aggravates the ischemic damage, resulting in the gangrenous aspect of the lesion tending to hide its ischemic origin. Indeed, the variability of the manifestations of the disease in one of its primary characteristics, and is a function of the different causative factors. A knowledge of the anatomy and pathophysiology of the splanchnic circulation and its hemodynamics is essential for a full appreciation of the diagnosis and treatment of the disorders, and for the adoption of the aggressive approach necessary to improve the poor prognosis of ischemic diseases of the colon and rectum. All treatment should be based on 1) constant, prolonged intensive care; 2) precise monitoring of any change in status; 3) rapid excision of any necrotic (often gangrenous) tissue. Ischemic colitis is most likely to occur in elderly patients with a history of cardiovascular disease, but can also affect younger individuals. It is a frequent, potentially lethal, entity. Although it can be classified as a separate disease on the basis of its clinical, radiological and anatomical characteristics, it is often confused with other disorders of the colon. Although the abdominal surgeon is most likely to be concerned with this disease, the vascular surgeon incising the lower aorta should always be on the look-out for segmentary ischemia of the distal colon which may occur following operation.

[Ischemic disorders of the large intestinal wall. Ischemic colitis and rectitis secondary to intrinsic vascular disorders]

Ischaemic diseases of the large intestinal wall is a characteristic syndrome caused by vascular insufficiency of varying degrees. The ischaemia results from haemodynamic disturbances and often arises in spite of the patency of the vessels. The mucosa of the intestine is the tissue layer that is most vulnerable to ischaemia. Ischaemia of the colon occurs in the presence of a microbial flora that is often highly pathogenic, and hence the lesions rapidly become infected. For this reason the inflammatory features of the disease tend to conceal its vascular origin and ischaemic colitis has often been confused with other infectious, inflammatory, ulcero-haemorrhagic disorders of the large intestine. Although the syndrome may occur in any patient, it is much more common in elderly subjects with a history of arteriesclerosis and cardiac disease. Two main varieties can be identified, depending on the extent of the vascular insufficiency. In the first, the lesion may heal spontaneously or evolve towards fibrous strictures of the colonic wall; in the second, gangrenous necrosis of the colon or rectum may develope, the clinical picture of which has more in common with an "acute abdomen' than with ulcerative disease of the colon.

Ultrasound patterns of disorders affecting the gastrointestinal tract

A mass associated with the gastrointestinal tract was detected by sonography in 33 patients. Etiologies included primary or metastatic tumor; intussusception; inflammation secondary to bowel infarction, pancreatitis, or irradiation; and a dilated, fluid-filled gut related to retained gastric contents, obstruction, ileus, or an ileal bypass. Mesenteric or omental changes were identified with inflammation and frequently with metastatic disease. The diagnosis was confirmed by repeat sonography, abdominal radiography, barium examination of the small bowel, computed tomography, surgery, or autopsy. Ultrasound patterns are characteristic in tumor, intussusception, and inflammation; specific features allowing differentiation between tumor and inflammation are described. Colonic haustra, valvulae conniventes, or bowel contours and peristalsis on real-time sonography are helpful in identifying fluid-filled bowel loops.

Intestinal blood flow at various intraluminal pressures in the piglet with closed abdomen

The influence of intraluminal pressure on intestinal blood flow was studied in two segments of the small intestine and two of large intestine ligated after insertion of intraluminal catheters in ten piglets. Intestinal segments were inflated in stepwise increments in intraluminal pressures of 15, 30, 45 and 60 mmHg and blood flow was measured with radioactive microspheres using four isotopes (Ce, Cr, Sr, Sc). Other segments were inflated to a pressure of 60 mmHg and then pressure decreased in a stepwise fashion to 30, then 0 mmHg for the last two injections. Small and large intestinal blood flow fell progressively with increasing intraluminal pressure. At 60 mmHg a forward flow of 25% of normal was still present. Furthermore, not only was there an absolute decrease in blood flow with increasing intraluminal pressure but this decrease was disproportionately large in the intestinal mucosa. A hyperemic response lasting approximately 15 minutes was observed after complete decompression. The intestinal blood flow distal to the ligated segments was always moderately increased as compared to intestinal blood flow proximal to the segments. The results reported herein are at some variance from other reported studies performed with the abdomen open and on isolated segment preparations. The reasons for these variations are discussed.

Correlation between retinal and pelvic vascular status: a determinant factor in patients undergoing pelvic irradiation for gynecologic malignancy

The degree of arteriolar sclerosis in pelvic vessels has previously been shown to be related to the incidence of radiation-related enteric and genitourinary injury. Retinal vessel changes were compared to pelvic vascular changes in 48 patients, half of whom were either diabetic or hypertensive. There was an absolute correlation between retinal vessel changes and bowel or cervicovaginal vessel changes in 74% of the cases, and only one patient had a marked (more than one grade) discrepancy between retinal and pelvic vascular status. The findings of this investigation suggest that funduscopic examination of the retina can provide useful information concerning the extent of vascular disease in structures normally present in the field of pelvic irradiation.

Non-occlusive ischemic colitis: angiographic aspects in a canine model

A model of non-occlusive colonic ischemia (NCI) was produced in the dog, incorporating both moderately decreases systemic pressure and increased intralumenal colonic pressure. These factors may play an etiologic role in human NCL. When differences between mean systemic and mean distention pressures were 30 mmHg or less, severe mucosal injury occured. In no case was the muscularis injured. Moderate systemic hypotension alone, or moderate colonic distention alone, did not produce significant colonic ischemic injury. Colonic distention with pressures of 60 mmHg alone resulted in colonic mucosal necrosis, but these pressures are beyond those ordinarily encountered clinically, even in large bowel obstruction. Angiography may be useful in demonstrating reduced flow to the colon during development of colonic ischemic injury. However, angiography is not a sensitive method in the diagnosis of nonocclusive colonic ischemic injury, once that injury has been established and inciting factors have subsided.

[Architectonics of the vessels of small and large intestinal grafts in esophagoplasty]

In experiments on 30 cadavers the structure of the small and large bowel vessels with the concern in esophagoplasty was studied. The angiography proved that in case of multiarcade structure of the small bowel vessels, more than in 50% of cases the great bowel showed a trunk type of the division of the vessels. In 70% of cases with a favourable structure of the small bowel vessels good conditions for taking a graft from the large bowel were found. In case of a relatively unfavorable or an unfavorable structure of the small bowel vessels (26.7%) there was the possibility to get a graft from the left side of the large bowel and in 50%--from the right one.

Acute ischaemic enteritis in Goa

Acute ischaemic enteritis is an uncommon condition which mainly affects young people. It is characterized by ischaemic changes in the small or large bowel which may be reversible in the early stages. The exact aetiology is not known. The condition may be due to toxins produced by either roundworms or Gram-negative bacilli or may be due to a localized allergic reaction. It is possible to make a preoperative diagnosis in most cases from the presence of abdominal pain, bloody diarrhoea and shock. Conservative treatment may be best in early cases but surgery is necessary in those cases where gangrene or perforation has occurred.

[Angina abdominalis: Clinical findings and therapy (author's transl)]

Angiographic and clinical findings of angina abdominalis are demonstrated by the clinical course of four patients. Two of them suffered from athero-sclerotic stenosis and the remaining two from compression of the coeliac trunc respectively the upper mesenteric artery by fibrotic strings. One patient was treated by an interposition of a saphenous vein graft another one by tissue decompression. Two patients were not operated upon, because one of them had sufficient collateral circulation on angiography, and the other denied an operation, he died one year after diagnosis because of an occlusion of the coeliac trunc and the upper mesenteric artery with following gangrene of the small and large intestine. Danger of complete intestinal necrosis following arterial vessel occlusion as well as reconstructive operative procedures on arterial occlusion should be considered.

[An unusual cause of an "intramural" gas collection in the right colon (author's transl)]

A case of subserous gas collection in the right colon following surgical repair of an iatrogenic uterus perforation is presented. The patient showed an ileus-like roentgen symptomatology when ischemic necrosis of the bowel was suspected. Laparatomy demonstrated the remainder of the gas collection in the area of the right pelvis extending retroperitoneally towards the right colon, thus presenting intramural pneumatosis. Therefore the differential diagnosis of intramural gas collection as a sign of ischemic bowel necrosis has to include the harmless subserous pneumatosis following abdominal trauma (especially iatrogenic uterus perforation).