Q. Why is my stool gray colored with a lot of undigested food in it?

Answered by
Dr. Ajeet Kumar Lohana
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Mar 29, 2021

Hi doctor,

I have had severe reflux since January and was just diagnosed with GERD and grade C esophagitis in February. At the time the reflux started, I began having yellow stool with a lot of undigested food in it. My stool has not been brown once since this started and there is always undigested food very clearly seen. On 3/5, I had a very gray, cement-colored stool mixed with the yellow and have had this several times since. The yellow is always soft and loosely formed or diarrhea. The gray pieces are sometimes small and sometimes large but always very hard and dry and always mixed with the soft yellow stool. I had an MRI with 3D MRCP on 3/1 that was unremarkable. On 3/3 I found out that I have two bacterial infections (Klebsiella oxytoca and Citrobacter braakii), for which I started herbal antibiotic treatment that day. On 3/5, I went to the ER because of the gray stool. I had taken a picture if someone said I just had anxiety and the doctor confirmed that when she sees stool that color, the first thought is biliary obstruction. My hepatic function panel tests were normal. My lipase was slightly elevated at 64 but was down 25 points from the previous week when it was 89. The gray stool has me very concerned that there is something going on with my life that might have been missed. If this were the case, by the time stool is gray due to liver issues, would something be showing up in bloodwork? I am particularly concerned that there is something wrong with my bile ducts, such as primary biliary cirrhosis? Is it possible to have symptoms of something like this with no evidence on MRI or bloodwork? Or can gray stool possibly be caused by bacterial infections? I have had hepatic panel tests as part of my yearly bloodwork for the last several years, and everything has always been perfect.



Welcome to

To be very honest, it is little strange that you developed GERD symptoms in January and developed Grade C esophagitis due to reflux. Since most of the patients with chronic GERD do have acid reflux symptoms for many years before having worsening symptoms and development of the esophagitis, if it were all of the recent onsets i.e. started just in January, with accompanying loose stools with undigested food, it make me think a condition like Zollinger Ellison syndrome (ZES). In this, there is hypersecretion of the gastrin hormone, which controls acid secretion from the stomach, which can lead to diarrhea, acid reflux, abdominal pain. Considering this possibility, I am more interested to see your endoscopy report. The answer to your concern about primary biliary cirrhosis (PBC) or any problem with bile ducts without evidence of abnormality on blood and radiologic test (MRI) is no. If there were any problem with your bile ducts, it should have shown on blood tests. However, MRI can be normal in PBC patients. But MRI is quite helpful in detecting any narrowing or stone of the bile duct or problem with the pancreas or pancreatic duct. Given normal MRI with MRCP (magnetic resonance cholangiopancreatography), I do not think the bile obstruction is the cause of gray color stools. You must remember, in diarrhea, the color of stool often changes from its normal yellow color because the gut does not have enough time to stain stools with bilirubin, so some change from normal is common and not a worrisome feature.

You can share the images of stools with me as I can appreciate whether it is pathological or just extreme of physiological color.

For ZES, I suggest you check morning fasting serum gastrin levels and show it to me when the report is available.

You can use video consultation to have a detailed discussion about your problem.

Best regards.

The Probable causes:

Rule out ZES.

Hi doctor,

I think I have had some form of reflux since August, hence the burning throat and tongue. I also realized that there was likely some undigested food prior to the severe symptoms as I would see a lot of what looked like grains almost daily, which I just thought was from eating corn chips, but it had never happened before. I was also taking 30 pills a day for three months prior to this happening at the direction of my naturopath. My gastroenterologist thought that might have contributed to the esophagitis. I tried drinking baking soda and water for a few days prior to the severe onset to help my burning mouth and tongue, which gave me two very bad bouts of diarrhea, and then the severe reflux started. From stool testing, prior to taking the PPI, my naturopath (a different one than the one that had me taking 30 supplements) thought my stomach acid was low and that, combined with the bacterial infections, caused the reflux. Do tumors in the pancreas or stomach not cause ZES? Could MRI not have picked those up? My gastroenterologist never mentioned it as a possibility and has talked about doing a colonoscopy, but I will ask about gastrin testing.

I have attached a picture of my stool. This is from the day I had the hepatic function tests.



Welcome back to

I have seen the photo you attached (attachments removed to protect the patient's identity). This basically contains lots of mucus (jelly), and given the history of taking baking soda, this gray color suggests necrosis or damage of the lining of the esophagus and gut. I also agree with your gastroenterologist that this is esophagitis that is probably caused by those neuropathy medicines, plus this baking soda. Baking soda is injurious to the gut lining. This is considered a strong alkali that can cause significant damage to the esophagus and gut lining. I strongly believe that this has caused all your miseries. You should start taking Calcium, Esomeprazole 40 mg twice daily for six weeks till the ulceration heals. Meanwhile, use liquid to a semi-solid diet. Avoid solid meals. If you feel significant pain in the esophagus or abdomen, go for CT enterography to assess the damage caused to your gut.

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