Skip to content
Link copied to clipboard

Medical Mystery: Dark stools trigger serious medical concerns

As a family doctor, I'm always on call for my own family.

As a family doctor, I'm always on call for my own family. So when my 82-year-old uncle called and told me his stools were black, my stomach did a little flip. Tarry black stools can be a sign of bleeding, usually from the upper gastrointestinal tract, and can imply ulcers, stomach cancer, or worse.

I knew he was in generally good health, hadn't smoked cigarettes for decades, and took medications for his blood pressure, prostate, and cholesterol. He did have occasional attacks of gout, for which he took anti-inflammatories. And I knew he liked a glass or two of wine most days. The anti-inflammatories and alcohol could combine to increase his risk of stomach bleeding, but his gout hadn't been active recently.

As calmly as I could, I asked him some more questions. He had no abdominal pain, nausea, or vomiting. His appetite was normal. His weight was stable, he had no pain with defecation, and no urinary complaints. I mentioned to him that various foods could produce alarmingly colored stools. Beets could resemble dark-maroon bleeding, but he denied having eaten anything out of the ordinary lately.

I told him he needed to contact his doctor. Even though he'd had a normal colonoscopy two years before, he needed some more testing. It was Saturday; could he wait until Monday to call his doctor? Yes.

On Sunday morning, he called and said his stools had reverted to their normal brown color. Was I still concerned, and did he still need to contact his doctor? Yes, I was, and, yes, he did.

He reported in a few days later: His doctor had ordered blood work before seeing him, and the results were back: his blood counts, iron level, liver function tests, electrolytes, and kidney functions were all normal. I felt a little better but was still anxiously awaiting word from his doctor.

Before the appointment, though, he called me back. My aunt had reminded him of something.


'Your aunt just reminded me that the day before this all started, I was pigging out on the cheap black caviar at an all-you-can-eat Chinese buffet. Could that have anything to do with this?"

I breathed a deep sigh of relief as I resisted the urge to burst out laughing.

Yes, I said, it did. Twenty-four hours of black stools after pigging out on black caviar was perfectly understandable. If his colonoscopy hadn't been so recent, it would have been prudent to repeat it. However, in the light of this new information, he didn't need any other investigations.

When I was in medical school, they drilled into us the importance of the patient's history in making an accurate diagnosis. When the clinical picture is unclear or confusing, the most fruitful course of action is to take more history. Find old hospital or clinic records, radiology reports, lab tests, or just go back and talk to the patient some more.

Even when patients try their hardest to help, they may not always know precisely what we physicians need to know to make the correct diagnosis. Frequently overlooked areas include travel history, dietary history, hobbies, pets, and the workplace environment. Toxic exposures, exotic organisms, and all kinds of other obscure etiologies often come to light when all of these historical avenues are thoroughly explored.

Sometimes, we need help from our patients to solve their mysteries.

Read more from the Check Up blog »