Thread by @john_damianosMD

🌬️ Breath testing for #SIBO: everything you need to know! 🎈 😮‍💨 💩 🦠 🐄 📈

#MedTwitter #medicine #science #GITwitter #GI #microbiome #IBS #diet #nutrition

cghjournal.org/article/S1542-…

To kick things off: how do you diagnose #SIBO?

#SIBO is a disorder characterized by excessive colonization of the small intestine by organisms usually found in the colon, especially Gram-negative bacteria.

(NB: the more we learn, it seems the *type* of bacteria is more important than the *number!*)

Side note on this point: it appears that it's the type of bacteria that underlie symptoms, not the absolute overabundance of microbes.

In fact, a healthy⬆️fiber diet can▶️#SIBO by numbers but not have any symptoms– it's because fiber promotes the GOOD🦠

nature.com/articles/s4146…

Symptoms of #SIBO are nonspecific and can include
🎈 bloating and distension
😣 abdominal pain or discomfort
💩 diarrhea or constipation (technically #IMO– more on this later)

Severe cases: malabsorption and deficiencies in fat-soluble vitamins and other nutrients (eg ⬇️B12)

🥇Gold standard diagnosis: jejunal aspirate
🦠 > 105 CFU/mL (more recently, a cutoff
of 103 CFU/mL has been advocated)

Problems:
💰expensive
🔦invasive
🦠difficult to do completely sterile (⬆️false positives)
📊lacking standard protocol

Breath testing principle:

🥤ingest fermentable carbohydrate (glucose 50–75g or lactulose 10g) ▶️ 🦠microbial anaerobic fermentation ▶️ 🌬️formation of gasses (H2, CH4, H2S) ▶️ diffuse into 🩸 ▶️ expired into 🫁 ▶️ measure breath 😮‍💨 every 15 minutes for 120 minutes

Defining a POSITIVE #SIBO breath test 👇

(⬆️10–12 ppm of H2 has been suggested to ⬆️ the sensitivity, without compromising specificity)

Since breath testing assesses byproducts of bacterial fermentation:
💊🚫antibiotics for 4 weeks
🔦🚫procedures requiring colon cleansing (colonoscopy) for 2 wks
💊🚫meds that affect motility (prokinetics, laxatives) for 1 wk
🍞🚫complex carbs, smoking, or exercise on the day of

Biggest limitation of BT: variability in the oral-cecal transit time (▶️false positives)

Since lactulose🚫absorbed in the small bowel it has ⬆️sensitivity for distal #SIBO. But it also⬆️false positives by detecting fermentation from normal colonic flora. H2 may be from colon🚫SB

Glucose is absorbed in the small bowel, so ⬇️ false positives.

This may be why we see ⬆️ positive tests for #SIBO in both #IBS and controls with lactulose compared to glucose.

journals.lww.com/ajg/Fulltext/2…

But glucose isn't perfect. 48% of positive glucose breath tests may be attributable to colonic fermentation of unabsorbed glucose. This is especially true in those with prior GI surgery.

Breath testing plus *scintigraphy* could help mitigate this risk of false positives.

So what substrate do you use for #SIBO breath tests?

There is no consensus on the optimal substrate.

Lactulose: sensitivity 42.0% and specificity 70.6%
Glucose: sensitivity 54.5% and specificity 83.2%

So glucose slightly>lactulose.

But ➕LBT predicts response to rifaximin in #IBS-D. (journals.lww.com/ajg/Fulltext/2…)

Both may be of use!

⚠️ Lactulose may be preferred in #diabetes (due to glucose ▶️ hyperglycemia and altered motility)

⚠️ Lactulose may be preferred in small bowel dysmotility, since glucose is less sensitive for distal #SIBO.

Switching gears to intestinal methanogen overgrowth!

Methanogens (such as Methanobacter smithii) ▶️ methane 🐄, which ▶️ #constipation.

Methanogens are not bacteria but archaea, so we can't say #SIBO, but #IMO.

#IMO has features different from #SIBO
👵⬆️age
🅱️⬇️likely to have B12 deficiency
💩⬆️likely to have constipation; ⬇️likely to have diarrhea
✂️🚫association with Roux-en-Y gastric
bypass, diabetes, or prior cholecystectomy (which are associated with SIBO)

cghjournal.org/article/S1542-…

Defining a positive CH4 breath test for #IMO 👇

What do breath test results look like?

1⃣H2 #SIBO
2⃣CH4 #IMO
3⃣negative test

journals.lww.com/ajg/pages/arti…

Side note:

Treatment of #SIBO: see table👇

Treatment of #IMO: rifaximin➕neomycin (methanogens are susceptible to older abx such as bacitracin and metronidazole, but more studies are needed)

Rotating antibiotics may be helpful, esp in dysmotility: onlinelibrary.wiley.com/doi/full/10.10…

Prokinetics may also be required when the underlying problem is small bowel dysmotility.

🧠 Remember, #SIBO is a reflection of some underlying process affecting one or more of our body's defense systems that maintain small intestinal homeostasis.

🔎 When you see #SIBO, ask WHY!

🔑 Take home points!

🌬️breath testing is a cost effective and noninvasive method to diagnose #SIBO & #IMO
🥤glucose & lactulose are both liable to false ➕ and –, though each may have a role depending on the patient
😮‍💨ensure proper protocol
👀stay tuned for new developments!

P.S. Need a refresher on all things #SIBO? Check out the @AmCollegeGastro guidelines!

journals.lww.com/ajg/pages/arti…

Also this recent @ANMSociety webinar:

Hope this was helpful!

#GITwitter #GI #microbiome #SIBO #IMO

@MarkPimentelMD @AliRezaieMD @RuchiMathurMD @gbsaff @BMoshiree @LindaNguyenMD @AGA_CGH @IBS_Maastricht @drkeithsiau @stevenbollipo @KewinSiah @drsarveemoosavi @doc_zubin @LucindaHarris16 @SultanMahmoodMD @JordanHaworth @WalterChanMD @ashish_chogle @mgrover_gi