Lymph fistula

Early work using the lymph fistula rat demonstrated that the amount of cholesterol appearing in intestinal lymph is directly proportional to the amount of dietary cholesterol present in the intestinal lumen [102]. Although less complete data are available in other species, this relationship also appears to be true in rabbit [103] and man [104]. Thus, in the post-absorptive state, after the intake of a diet containing substantial amounts of sterol, most cholesterol in intestinal lymph is probably derived from the diet [98]. 

Fig. 12. Appearance of newly synthesized cholesterol in mesenteric lymph of the rat. The experimental animals had indwelling lymph fistulae and were infused intraintestinally with a glucose-amino acid-electrolyte solution. One group of these animals was also administered intravenously chylomicrons containing lOS mg of cholesterol, while another group was infused intraduodenally with com oil. 24 h after the initial surgery, each animal was administered [ H]water intravenously and the secretion of labeled cholesterol in intestinal lymph was followed for 18 h. The amount of [ HJwater incorporated into cholesterol was used to calculate the amount of newly synthesized cholesterol present in lymph. These values are expressed as the nmoles of newly synthesized cholesterol secreted into the lymph each hour. The data points represent means +1 S.E.M.

The mechanism of the inhibition of the HMG-CoA reductase by bile adds shown in Fig. 14 is a matter of controversy. Weis and Dietschy did not observe any influence of taurocholate on cholesterol synthesis in bile fistula rats fed a cholesterol-free diet, and concluded that the inhibitory effect of bile acids on cholesterol synthesis may be related to the increased absorption of cholesterol by the presence of bile acids in the intestine [247]. However, Hamprecht et al. were able to demonstrate a reduction of HMG-CoA reductase activity in lymph fistula rats infused with cholate [248]. Results by Shefer et al. also indicate that bile acids inhibit HMG-CoA reductase directly [212]. It seems likely that the inhibitory effect of the bile acids on HMG-CoA reductase may involve both direct and indirect effects. It was recently established that the stimulation of HMG-CoA reductase activity in response to treatment with cholestyramine is associated with an increase of the specific mRNA [258]. 

The lack of blood supply restricts the use of in vitro preparations to short-time incubation studies only. Long-time experiments which allow determination of lipid absorption under steady-state conditions can be performed by perfusion of an intestinal segment in situ or by infusion of lipids into the duodenum of a rat with a lymph fistula. A comparison of in vitro and in vivo techniques has been made by Clark [54]. 

It is well estabUshed that uptake of oleic acid from an emulsion is significantly reduced compared to uptake from a micellar solution. This has been shown in vitro with everted sacs of rat jejunum [78] as well as in vivo with lymph fistula rats [72]. 

Tso, P., Ding, S., DeMichele, K. and Huang, Y.-S. (2001) Intestinal absorption of high y-linolenic acid canola oil in lymph fistula rats, in y-Linolenic Acid Recent Advances in Biotechnology and Clinical Applications (eds Y.-S. Huang and V.A. Ziboh), AOCS Press, champaign, pp. 321-334. 

The frequently met statement that the major portion of absorbed fat passes into the lymph stream stems from the classical experiments performed by Munk and Rosenstein in 1891 on a patient suffering from elephantiasis, in whom a lymphatic fistula developed in the left leg. From such a fistula, these workers were able to recover as much as 60% of the fat of an ingested meal. Ever since the appearance of this report, much time has been expended in a search for the path of absorption of the 40 % that was not recovered from lymph fistula. Recent work with labeled fats has shown, however, that this search was unnecessary, at least so far as long-chain fatty acids are concerned. 

Murata etal. (1994) reported that the release rate of resynthesized TAG into the intestinal lymph was lower after the administration of a DAG emulsion than a TAG emulsion (Murata et al, 1994). Six lymph fistula rats were continuously infused with either a DAG emulsion [containing 65.6% (w/w) 1,3-DAG and 32.6% (w/w) 1(3),2-DAG] or a TAG emulsion at the rate of 1 ml/h for 1 h through a canula inserted into the stomach. The amount of test oil in each test emulsion was adjusted so that both emulsions delivered equal amounts of fatty acids (144 mg/h). Lymph fluids were collected every hour for 5 h after starting infusion of the lipid emulsions, and lymph chylomicrons were isolated, purified and analysed. 

Crandall, L. A., Barker, S. B., and Graham, D. G. (1943). A study of the lymph flow from a patient with thoracic duct fistula. Gastroenterology 1, 1040-1048. 

Vitamins K and Kj are absorbed by an active process in the proximal small intestines. Bile of normal composition is necessary to facilitate the absorption. The bile component principally concerned in the absorption and transport of fat-soluble vitamin K from the digestive tract is thought to be Jcoxycholic acid. The molecular compound of vitamin K with deoxycholic acid was effective on oral administration to rats with biliary fistula. Vitamin K is absorbed through the lymph in chylomicrons. It is tran.sportcd to the liver, where it is concentrated, but no significant storage occurs. 

Ulcerative colitis is confined to the rectum and colon, and affects the mucosa and the submucosa. In some instances, a short segment of terminal ileum may be inflamed this is referred to as backwash ileitis. Unlike Crohn s disease, the deeper longitudinal muscular layers, serosa, and regional lymph nodes are not usually involved. Fistulas, perforation, or obstruction are uncommon because inflammation is usually confined to the mucosa and submucosa. 

Leg edema as a consequence of lymph node involvement, thrombophlebitis, fistula formation, weight loss, and pain in the lower back or radiating down the legs are indicative of widespread disease. 

Data on absorption of non-micellar lipids in the presence of bile salts is available from the study )y Knoebel [79]. The lymphatic transport of absorbed oleic acid and site of uptake from the intestinal lumen was measured in bile fistula rats. It was found that the concentration of bile salts in a continuous intraduodenal infusion did not affect the steady-state level of lipid appearing in the lymph until the bile salt concentration was as low as 1 mM, which represented a molar ratio of 20 1 of lipid to bile salt. In the case of infusates with relatively low concentrations of bile salts it was found that a larger part of the available surface area of the small intestine was utilized. The main conclusion is that lipids are equally well absorbed in vivo from non-micellar dispersions of lipids and bile salts as from solutions where the lipids are completely solubilized by bile salt mixed micelles. However, a detailed analysis of kinetics of uptake from non-micellar phases in vitro with isolated intestinal segments has not yet been done. 

The US manifestations of CD reflect the pathological features, consisting of abnormalities of bowel wall or representing its intra-abdominal complications. The abnormalities of bowel wall include bowel wall thickening, alterations of bowel wall echo pattern, hyper-aemia, loss of elasticity and peristalsis, mesentering hypertrophy and mesenteric lymph nodes. Intraabdominal complications of CD typically include stenoses and obstruction, fissures and fistulae, as well as inflammatory masses (phlegmon or abscesses). 

Radiotherapy consists of external beam irradiation of the uninvolved pelvic lymphatics and uninvolved parametrial tissue with a dose of up to 45 Gy and intracavitary brachytherapy with three to six fractions of 4-8 Gy each dehvered to point A or the uterus [62], corresponding to a total dose equivalent of 70-80 Gy delivered to point A. The dose delivered by external beam radiotherapy is adjusted to the local tumor extent and metastatic nodal involvement (boost). A larger field of external irradiation is chosen in patients with para-aortic lymph node metastases. No brachytherapy is done in most patients with infiltration of the bladder or rectum because of the risk of fistula development. Alternatively, cervical cancer with invasion of adj acent pelvic organs can be treated by surgical pelvic exenteration. The most common therapies according to stage are summarized in Table 7.3. 

The obligatory role of bile acids in the overall process of cholesterol absorption has been largely documented both in animals and in humans. In 1952 Siperstein et al. showed that when labeled cholesterol was given to bile fistula rats virtually no radioactivity was recovered in the thoracic duct lymph in the following 24 hours [32] In keeping with these animal studies Quintao et al. reported that when one patient with primary biliary cirrhosis and complete biliary obstruction was given Ig of cholesterol/day - dissolved in a liquid formula fatty diet - no cholesterol was absorbed[77]. Similarly, dietary cholesterol absorption was significantly lower than normal in patients with advanced liver cirrhosis, who had a marked reduction of total bile acid pool size[88]. 

Primary tuberculosis of stomach and duodenum is very rare and usually develops secondary to pulmonary tuberculosis. Simultaneous involvement of the duodenum occurs in 10% of patients. There is increased incidence in patients with AIDS. The radiological appearances are classified as predominantly ulcerative or hypertrophic type (Tishler 1979 Agrawal et al. 1999). The ulcerative form is more frequent and consists of multiple large and deep ulcerations, sometimes with antral fistulas (Fig. 5.10). In the hypertrophic form, there is thickening of stomach and duodenal folds which can lead to pyloric stenosis and gastric outlet obstruction. A narrowed antrum can mimic a linitis plastica appearance. There is usually extensive lymph node involvement in the adjacent areas (Tishler 1979 Agrawal et al. 1999). Sarcoidosis and syphilis have identical appearances on conventional barium studies, both ulcerative and hypertrophic (Fig. 5.11). 

In addition to those associated with fistulas and perigraft abscesses discussed above, these fluid build-ups can be constituted of blood and/or lymph. Postsurgical lymphorrhea causing a lymphocele is avoided, above all by preventive measures. This complication is even more unusual when vessel dissection is limited during the transplantation and combined with careful lymphostasis. Should it occur early despite those precautions, drains should be kept in place for several days to avoid collection formation. 

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