post hoc ergo propter hoc
General Internal Medicine Conference
Case Presentation
April 16 2008
Pedro Salinas
HPI
 60 y/o woman with h/o IBS
 3 week h/o vomiting, diarrhea and right upper
quadrant pain
 10 episodes/day watery stools, maladorous,
non-relieved by fasting. No blood or mucus
seen
H&P Cont..
 Last colonoscopy 2 year ago (OSH), which
reported normal per patient
 PMH
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HTN
h/o PE
RA-seronegative
Osteopenia
Raynaud’s
Migraines
IBS
Benign breast mass
GERD
 1995 Diagnosed with Undefined Connective
Tissue disease. Seronegative . High
inflammatory markers
 2002 GI Nausea, weight loss. CT pancreatic
head fullness
 Normal ERCP and pancreatogram
 2005 EGD and EUS
Home Medications
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ASA 81 mg PO qd
Lisinopril 10 mg PO qd
Metoprolol 50 mg PO bid
Simvastatin 40 mg PO qhs
MVI PO qd
Amitriptylline 50 mg qhs
Ca/Vit D PO bid
FiberCon PO qd
Nifedipine ER 90 mg PO qd
H&P Cont..
 Allergies: Penicillin and Naproxen
 FamHx: Father died age 64 from massive
stroke. Mother died age 69 lung cancer. No
colon cancer.
 SocHx:Lives at Friendship, WI. +tobacco
1ppd. 1-2 drinks/wk. No illicit drug use.
H&P Cont..
 T 97.7 HR 100 RR 16 BP 138/73 O2 98% on RA
 HEENT: PERRLA, EOMI, no oral lesions. No
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thyromegaly.
CV: PMI non-diplaced, RRR, S1/S2 3/6 SEM
radiating base neck
Lungs: CTAB
Abdomen: Mild tenderness RUQ. No
guarding. +BS
Ext: no edema. Skin: no rash.
 Addendum written that morning on record:
 I saw….. Prolonged course for her typical
IBS… Will contact GI for need to investigate
for microscopic colitis……
 On GI Consult Note:
 Reason for consultation: Diarrhea
Labs
 CRP 8
 Normal Stool Gap
 Guiac neg.
 C diff. Neg
 TTG Antibodies Neg
Microscopic Colitis
 Lymphocytic colitis and collagenous colitis
 Sixth decade of life
 CC 10-15.7/100 000 LC 14.2/100 000
 Female:male
 ratio 7:1 in CC and 2:1 in LC
 Concomitant autoimmune diseases
Microscopic colitis
 Chronic non-bloody diarrhea, abdominal
pian, weight loss. Fatigue, nausea and fecal
incontinence.
 Enteropathic arthritis in 7%, seronegative and
nonerosive
 Clinical course is most often chronic relapsing
and benign
 Macroscopically normal or near normal
mucosa
Histopathology
 Microscopic assessment of colonic mucosal
biopsies
 Edema, erythema or abnormal vascular
pattern 30%
 Colagenous colitis: thickening of subepithelial
collagen layer beneath basal membrane
 Lymphocytic colitis: characteristic increase in
intraepithelial lymphocytes >20 IEL/100
epithelial cells
Treatment
 Cochrane Database Review 2007
 Only one RCT with Bismuth with clinical
improvement but not statistically significant
or histologic improvement
 Mostly anecdotal evidence and extrapolation
from collagenous colitis
Confirmation Bias
selective focus upon evidence that supports
their beliefs or what they want or believe to
be true, while ignoring evidence that serves
to disconfirm those ideas
Francis Bacon described
confirmation bias as follows in
1620
The human understanding when it has once
adopted an opinion (either as being the received
opinion or as being agreeable to itself) draws all
things else to support and agree with it. And
though there be a greater number and weight of
instances to be found on the other side, yet
these it either neglects and despises, or else by
some distinction sets aside and rejects; in order
that this great and pernicious predetermination
the authority of its former conclusions may
remain inviolate