Colon questions 21-30

21 A

Investigations in lower GI bleed should be specific and less time consuming

Small bowel enteroclysis, which uses a tube to infuse barium, methylcellulose, and air directly into the small bowel, yields better images than simple small bowel follow-through. Because the yield has been reported to be very low and the test is poorly tolerated, it is now rarely used.

Capsule endoscopy uses a small capsule with a video camera. capsule endoscopy is an excellent tool for the patient who is hemodynamically stable but continues to bleed, with reported  success  rates  as  high  as  90%  in  identifying  a  small bowel  pathology.

The hemodynamically stable patient should undergo small bowel enteroscopy. Usually performed with a pediatric colonoscope, it is referred to as push endoscopy. It can reach about 50 to 70 cm past the ligament of Treitz  in most cases and permits endoscopic management of some lesions. Overall, push enteroscopy is successful in 40% of patients .

Double-balloon endoscopy is another technique gaining in popularity. Although technically difficult, this approach is capable of providing a complete examination of the small bowel. In expert hands, double-balloon enteroscopy can identify a bleeding source in 77% of cases with occult bleeding, with the yield increasing to over 85% if the endoscopy is per-formed within 1 month of an overt bleeding episode.The advantage of this technique is that as well as visualization,  biopsies can be performed and therapeutic interventions undertaken.

To conclude investigations in lower GI bleed have to be specific and have high sensitivity also.

Sabiston

22 b 

Endoscopic  reduction  of  sigmoid  volvulus  should  be  attempted  in  patients  without  evidence  of bowel  necrosis  or  perforation. An  abdominal  radiograph  should  be obtained  following  endoscopic  detorsion  to  confirm  resolution  of  the  volvulus.

A  variant  of  cecal  volvulus  termed  cecal  bascule  is  a condition  in  which  a  mobile  cecum  folds  interiorly  and superiorly  over  a  fixed  ascending  colon  without  rotation on  the  vascular  pedicle. Although  local  ischemia  and  infarction  have been  reported,  vascular  embarrassment  occurs  less  frequently.

23 d  left colic artery 

Left  colon  replacement  of  the esophagus - Blood  supply  is  provided  through  the  inferior mesenteric  artery,  the  left  colic  artery,  and  the  anastomotic  branch connecting  the  middle  colic  artery.  The  middle  colic  artery  is  divided  near  its  origin  from  the  superior  mesenteric  artery. 

For complete mobility of the hepatic flexure, hepatic  flexure,  the  right  colic  vessels  often  must  also  be divided.

Short segment colon transposition- The  most  popular  segment  of  colon  to  use  for distal  esophageal  replacement  is  an  isoperistaltic  segment of  the  distal  transverse  colon  or  the  descending  left  colon based  on  the  ascending  branch  of  the  left  colic  artery.

Best colonic interposition graft is left hemi colon with isoperistaltic anastomosis. It is because of two reasons. First its blood supply is robust and dependable and 2nd because of the size match. Presence of marginal artery between left branch of middle colic artery and ascending branch of left colic artery is critical. Left hemi colon graft is completely based on left colic artery.

Middle colic artery is ligated. Right colic artery is also ligated.  This is for left hemi colon graft.

The question states that transverse colon is used for colonic interposition. Short segment transverse colon grafts are based on middle colic artery.

24. a

Crohn disease activity index is a medical tool, which helps to quantify the symptoms and problems of Crohn's disease

It helps to quantify the disease

It helps to assess response to medical therapy

Crohn's disease activity index includes

• Number of liquid or soft stools per day for 7 days - X 2
• Abdominal pain graded from 0-3 based on severity each day for 7 days - X 5
• General well being assessed from 0-4 -  X 7
• Presence of complications (extraintestinal manifestations) - X 20
• Taking diphenoxylate/loperamide/opiate/atropine for diarrhoea - maximum weightage- X  30
• Presence of an abdominal mass - X 10
• Hct of < 0.47 in men and <0.42 in women - X 6
• % of deviation from standard weight - X 12

25) b

MOderate differantiation

Poor prognostic factors in a polyp aare

1. histologically  poorly  differentiated invasive  carcinoma

2. cancer  cells  observed  in  the lymphovascular  spaces,  there  is  a  more  than  a  10%  chance  of metastases   

3. A pedunculated  polyp  with  invasion  to  levels  1,  2,  and  3  has  a  low risk  for  lymph  node  metastasis  or  local  recurrence  and  complete excision  of  the  polyp  is  adequate  if  the  poor  prognostic  factors mentioned earlier are absent .

4. A sessile polyp containing invasive cancer  has  at  least  a  10%  chance  of  metastasis  to  regional  lymph nodes ,  but  if  the  lesion  is  well  or  moderately  differentiated,  there is  no  lymphovascular  invasion  noted,  and  the  lesion  can  be completely  excised,  the  depth  of  invasion  by  the  cancer  may provide  useful  prognostic  information. 

There  is  a  high  risk  for lymph  node  and  distant  metastases  associated  with  sessile  cancers in  the  rectum,  and  these  lesions  should  be  treated  aggressively.

26) a

Arthritis,  ankylosing  spondylitis,  erythema  nodosum,  and  pyoderma  gangrenosum  typically  improve  or  completely  resolve after  colectomy.

PSC  occurs  in  5%  to  8%  of  patients  with  ulcerative  colitis. 

HLA-B8  or HLA-DR3  haplotype  are  10  times  more  likely  to  develop  PSC. 

The  risk  for  colon  cancer   in these  patients  is  up  to  five  times  greater   than  in  patients  with ulcerative  colitis  alone.  These  tumors  are  more  likely  to  arise proximal  to  the  splenic  flexure . Colectomy  has  no  effect  on  the course  of  PSC.

27 ) a

Anterior Resection

Cancers 6 cm above dentate line are considered to be upper ectum. Patients  with  cancer  of  the  upper  part  of  the  rectum  or  rectosigmoid  are generally  treated  initially  by  surgical  resection,  and  adjuvant  therapy.

  Sphincter-preserving  resections  of  the  rectum  are referred  to  as  anterior  resection,  low  anterior  resection  (LAR), or  low  anterior  resection  with  coloanal  reconstruction. 

In general,  anterior  resection  refers  to  resection  of  the sigmoid  or  rectosigmoid .  LAR  is  used to  refer  to  anterior  resection  combined  with  complete clearance  of  the  pelvic  side  walls. Anterior resection is excision of  proximal  rectum  or  rectosigmoid  above  the peritoneal  reflection. 

The  term  low  anterior  resection  indicates that  the  operation  entails  resection  of  the  rectum  below  the peritoneal  reflection  through  an  abdominal  approach.

Local excision has is done for lesions which are T1 and upto 10 cm from the anal verge.

28) a

Lynch  syndrome  is  an  autosomal  dominant  familial  Colo Rectal Cacner  syndrome  characterized  by  familial  clustering  of  early age-of-onset  CRC  (average  age,  40  to  48  years),  as  well  as a  variety  of  other  cancers.

First  two  MMR  genes  to  be  identified  were  MSH2 and  MLH1.  Each  of  these  proteins  forms  a  heterodimer with  so-called  minor  partners,  MSH6  and  PMS2. 

In  contrast  to the  chromosomal  abnormalities  associated  with  the classic  adenoma-to-carcinoma  sequence,  the  genetic changes  associated  with  MMR  mutations  are  more  subtle. MLH1   is  the gene  most  likely  to  be  affected   in  this  way  in  sporadic cases  of  MSI-H  colon  cancer . Microsatellite  instability  is  of  prognostic  significance in  colon  cancer. Patients  with  MSI-H  colorectal  cancer  have  a  better  prognosis  when  compared  to  patients  with microsatellite-stable  tumors  of  similar  stages.The absence  of  MMR  proteins  may  also  predict  decreased responsiveness  to  5-fluorouracil–based  chemotherapy.

Ref Shackelford 

29) a

Low specificity 

With a reference value of 5 ng/ml, the sensitivity of CEA was at 37% only for patients with colorectal carcinoma at Dukes B stage, 66.6% for patients at stage C, and 75% for patients at stage D. The specificities of the CEA for the cancers of the colon and rectum were at 76.98% with a reference value of 5 ng/ml and 86% with a reference value of 10 ng/ml 

HIgh preop value - poor prognosis

Follow up after surgery is 6 monthly

30)d

The gene is expressed in 100% of patients with the mutation.  Approximately 25% of patients with FAP have no knowledge of a family history of the disease. Reasons for this include adoption, deliberate withholding of information by affected family members, nonpaternity, germline mosaicism, and a de novo mutation at conception

SKF page 1963

Attenuated FAP is a milder form of classic familial adenomatous polyposis (FAP) and is characterized by fewer colon polyps (an average of 30) and a delay in the development of colon cancer (average age 50 to 55 years) (True) aFAP is caused by mutations in the APC gene and is inherited in an autosomal dominant manner. 

In practical terms, the decision for IRA or IPAA is driven by the severity of the polyposis: the more severe the polyposis the higher the risk of metachronous rectal polyposis and/or rectal cancer. When there were 5 or fewer rectal adenomas and 1000 or fewer colonic polyps, no patient needed a subsequent proctectomy. When there were 6 to 20 rectal adenomas, 15% of patients needed later proctectomy; however, with 20 or more rectal adenomas, the incidence of later proctectomy was more than 50%.

Choice c is correct

SKF 1966

attenuated FAP has extracolonic involvement most commonly duodenum and so d is false