A conversation with ChatGPT about my stool -shape, size, colour, symptoms and a possible diagnosis.

My request after initial info was dismissed as “never heard of ”

I would like a deeper medical explanation and reference to scientific papers as my physician has never heard of this diagnosis

ChatGPT said:

Thought for 12 seconds

Great — I’ll give a focused, medically detailed explanation (why this can happen), the tests that detect it (and their limits), how clinicians commonly confirm it in practice, and a short suggested phrasing you can hand your physician. I’ll cite primary review/meta-analyses and well-accepted resources so your doctor can check the literature quickly.

Short summary (one line)

Your pattern — sudden, dark-brown, pasty stool with quicker transit and normal routine stool tests — is most consistent with mild/partial pancreatic exocrine insufficiency (PEI) or a rapid-transit state that reduces mixing/time for digestion, both of which can produce pasty stool without frank steatorrhea and can be missed by routine stool testing. NCBI+1

1) Why this happens — physiology (clear, stepwise)

Fat digestion needs pancreatic lipase (and co-factors) released into the duodenum. If that enzyme delivery is reduced (even mildly), dietary fat is not fully broken into micelles for absorption. That changes stool texture even if it doesn’t produce full steatorrhea. NCBI
Transit time matters. If intestinal transit is faster, stool spends less time in the small bowel and colon for mixing, hydrolysis, and water handling, so partially digested material (pasty, sticky) passes sooner and appears darker/pasty rather than pale, bulky steatorrhea. Large cohort work shows stool consistency and microbiome strongly correlate with transit time. Gut+1
Together, a small fall in exocrine pancreatic output + faster transit can produce dark brown, pasty stool without the classic oily, floating stools of severe fat malabsorption — and routine stool cultures/occult blood tests won’t detect this. NCBI

2) Tests available (what they measure, strengths, limits)

Fecal pancreatic elastase-1 (FE-1) — a common noninvasive screening test for pancreatic exocrine insufficiency. Good as a first test but sensitivity is moderate (misses mild cases) and results must be interpreted in clinical context. Meta-analyses show pooled sensitivity ~0.77 and specificity ~0.88 vs. direct pancreatic tests. PubMed+1
72-hour fecal fat collection / Coefficient of Fat Absorption (CFA) — the classical gold standard for quantifying fat malabsorption (measures grams of fat lost in stool). It’s more sensitive for mild fat malabsorption but cumbersome for patients and not always ordered. PMC
Direct pancreatic function testing (secretin stimulation test) — more accurate but invasive/less available; typically used by specialists. FE-1 compares reasonably but is less accurate for mild disease. PubMed
13C-mixed triglyceride breath tests and other specialized tests — used in research/tertiary centres; less widely available but can detect milder dysfunction. PMC
Imaging (abdominal ultrasound / CT / MRI pancreas) — used if structural pancreatic disease is suspected (chronic pancreatitis, mass). Many older adults have low-grade dysfunction without clear imaging changes. NCBI

3) How clinicians commonly confirm the problem in practice

Step 1: Order FE-1 as a screening test (easy stool test). Understand that a normal FE-1 does not fully exclude mild/early PEI. PubMed
Step 2: If clinical suspicion remains high despite a normal FE-1, either order a 72-hour fecal fat (to quantify fat loss) or refer for specialized testing (13C breath, secretin test) or imaging. PMC+1
Step 3: Therapeutic trial of pancreatic enzyme replacement therapy (PERT) (short trial of standard doses with meals) is commonly used in practice: improvement in stool consistency and symptoms on enzymes is both diagnostic and therapeutic when tests are equivocal. Guidelines and reviews discuss PERT as part of management. NCBI

4) Why your physician “may not have heard of it” (how to explain)

PEI is most commonly discussed in the context of chronic pancreatitis or cystic fibrosis, but mild exocrine dysfunction in older adults is a documented, underrecognized phenomenon and may present atypically (pasty stool, normal routine tests). Population studies and geriatric research have measured lower fecal elastase in some older adults without other disease. jgld.ro+1

5) Differential diagnoses to consider (brief)

Small intestinal bacterial overgrowth (SIBO) — usually causes gas/bloating/abdominal discomfort, so less likely here but still possible. NCBI+1
Bile acid diarrhea/malabsorption — tends to cause watery diarrhea rather than sticky pasty stool. PMC
Medications, celiac disease, IBS with rapid transit are other possibilities (your history argues most strongly for mild PEI/rapid transit interplay). NCBI+1

6) Recommended stepwise plan you can discuss with your physician

(Use this wording if you want to hand them a short checklist.)

Order fecal pancreatic elastase-1 (FE-1) as an initial screen. (If positive/low, it supports PEI.) PubMed
If FE-1 is normal but suspicion remains, request either 72-hour fecal fat (CFA) or referral for specialized testing (13C-mixed triglyceride breath test or secretin stimulation testing at a gastroenterology service). PMC+1
Consider a monitored therapeutic trial of pancreatic enzyme replacement therapy (PERT) (standard dosing at meals) for 1–2 weeks to see if stool texture normalizes — improvement supports mild PEI as the cause. (This is commonly used in clinical practice.) NCBI
If PERT helps, continue under physician supervision and consider checking weight, fat-soluble vitamin levels (A, D, E, K) if problems recur. If PERT does not help, proceed with evaluation for SIBO, bile acid issues, or imaging. NCBI

7) Suggested text you can give your physician (copy-paste)

“I’ve had a sudden change to dark-brown, pasty stool with quicker bowel transit. Routine stool tests were normal. I’m concerned about mild pancreatic exocrine insufficiency (PEI) or a rapid-transit state causing incomplete fat digestion. Could we check fecal pancreatic elastase-1 and — if that’s normal but clinical suspicion remains — consider 72-hour fecal fat or a short therapeutic trial of pancreatic enzyme replacement (PERT)? I can provide references if useful.”

(If you’d like, I can draft a one-page PDF with the short references for your doctor.)

8) Key citations (for your physician)

StatPearls / NCBI: overview of Pancreatic Insufficiency (symptoms, diagnosis, management). NCBI
Vanga et al., meta-analysis — diagnostic performance of fecal elastase-1 (sensitivity/specificity; limitations for mild disease). PubMed
de la Iglesia et al. / UEG review on diagnostic accuracy and role of CFA vs FE-1. PMC+1
Herzig et al. / BMC Geriatrics: fecal elastase levels in older individuals (shows age-related findings and relevance to geriatrics). ResearchGate+1
Gut (BMJ) studies on transit time and stool consistency / microbiome (supports the physiology linking faster transit to changed stool texture). Gut+1

If you’d like, I can now (pick one):

Draft a one-page, physician-friendly summary with the five citations (PDF) you can hand or email to your doctor; or
Draft the exact message/email you can send to your physician or their nurse; or
Outline a specific PERT trial regimen (dosing, what to expect, safety notes) you can discuss with the doctor.

Which would you prefer?

ChatGPT and me