In some parts of the world, a toilet is dramatically different from the standard porcelain, plastic, or stainless steel common to American bathrooms. A trip to the Far East exposed me to many exotic sights, including a loo solely consisting of a ceramic square with a hole between two footrests. In Shenzhen, my hotel room toilet had more controls than a small jet. But like the interest we make on cash deposits, our throne deposits should interest us.
As pilots, we are trained to notice the smallest abnormalities: a faint vibration, abnormal gauge readings, changed performance; ignoring those cues risks having a bad day. Your body operates on the same principle, and stool is an underappreciated indicator of numerous disease processes.
Form follows function; we can look at an aircraft and appreciate that a particular shape suggests speed, maneuverability, ceiling, and so on. Same thing for your poop. In general, any recent change in stool shape, size, or frequency merits a visit to the maintenance hangar where your human A&P will evaluate what needs attention. And report if this squawk is accompanied by unexplained weight loss, fatigue, fever, night sweats, abdominal pain, or a family history of colorectal cancer. This is the human version of multiple red panel warning lights.
There is a new movie called Constipated, but it hasn’t come out yet. Very hard, pellet-like stools are most often a sign of dehydration, common in pilots, as cockpit air is dry and respiratory rate increases with altitude. We also tend to restrict fluids when flying, thereby avoiding inconvenient lavatory breaks. Poor dietary fiber intake or certain medications like codeine can change fecal shape, as can chronic constipation, although if taking codeine, you should not be flying anyway. I have previously addressed diverticulosis and colorectal cancer, two common causes. Chronic constipation can also lead to hemorrhoids, fissures, and fecal impaction, all of which are distracting and unpleasant at best, and grounding at worst.
Loose or watery stools suggest infection, food intolerance, inflammatory or irritable bowel diseases, or medication effects. From an aviation perspective, if you are going to the toilet all the time, it’s a clear no-go indication; if your bowels are making uncommanded control inputs, you should not be taking command in the cockpit.
Chronic, high-volume diarrhea raises concern for malabsorption syndromes such as coeliac disease and various infections or parasitic infestations. Other conditions like pancreatic insufficiency or endocrine disorders such as hyperthyroidism can also affect the gut. These conditions often sneak up gradually, like a slow fuel leak, until range and performance are clearly compromised.
Persistent ribbon-thin or pencil-shaped stools may indicate narrowing from a tumor or stricture in the lower colon or rectum. Disturbed airflow over the wing can disrupt lift—so if you see such dodgy number twos, lift your derriere and report to ATC—anus traffic control.
You may well have heard the joke about Braniff’s brown livery; on ground frequency, a taxiing pilot asked the Braniff cockpit crew, “What did you fly through up there?” Normal stool is brown, reflecting healthy liver metabolism. Any other color should grab your attention.
Pale, clay, or putty-colored stools suggest flow of bile from the liver is impaired and may be caused by gallstones, a tumor obstructing flow, or pancreatic disease. These stools are often accompanied by dark urine, itching, and jaundice. This is a major squawk and merits a high-speed taxi to maintenance.
Black, tarry stools, melena in medical speak, indicate upper gastrointestinal bleeding from ulcers, tumors, gastritis, or varicose veins in the gullet, stomach or upper small bowel. In addition to their appearance, they stick to the toilet, are hard to flush, and stink to high heaven. This is a medical emergency; flying with melena is the physiological equivalent of continuing flight with zero oil pressure.
Bright red blood usually originates from the lower gastrointestinal tract. If on the toilet paper only, it often points to hemorrhoids or fissures, but if mixed in with the excrement it raises concern for something lurking in the rectum or colon. If colored maroon, it suggests bleeding higher up, in the lower small bowel or first part of the colon. If you have consumed beets in the past day, that can give a red hue to poop. Incidentally, while researching this article I discovered some great products, and in disclosure, I have no financial connection to any of these! The first is Bumboo, sustainable toilet paper made from bamboo (softer than the plant it originates from, I believe); in Wales they recycle manure into SheepPooPaper, and in Sri Lanka, they do the same with elephant dung.
Green stools imply rapid intestinal transit, but iron supplements, certain antacids, and food dyes can also do this. If transient, it is usually a benign cause, such as a case of traveler’s diarrhea or eating something that disagreed with your gut. You know about the chap who ate a can of alphabet soup? He had the biggest vowel movement ever.
Greasy, bulky, foul-smelling stools that float and stick to the toilet are classic steatorrhoea, indicating fat malabsorption. Causes include failure of the pancreas and celiac disease. Untreated, malabsorption can lead to nutritional deficiencies that impair cognition, reaction time, and endurance, not attributes favorable to aviators! And if one sees undigested food, this may reflect rapid transit or enzyme deficiency, akin to unburned fuel exiting the exhaust.
Mucus may appear in small amounts in irritable bowel syndrome, but persistent mucus—especially with blood—raises concern for a diagnosis of Crohn’s disease or ulcerative colitis, serious conditions that merit urgent investigation and treatment. Bowel cancer can present in this way as can benign growths, some of which can pump out so much potassium-rich mucus it can lead to heart rhythm issues or even cardiac arrest. Pus should never be seen in the bowl and suggests severe infection or inflammation.
If one has an urge to visit the throne room, but nothing happens, we call that tenesmus—it implies there is something lurking in the rectum sending false messages to your brain. This symptom should never be ignored as it suggests either inflammation or a tumor. Needing to occupy the Sovereign’s chair at night is concerning, and strongly suggests something is going haywire, either with gut structure or function.
Just as pilot training affects how we perform in later years, how our gut is trained as a baby impacts future health. Even the very first stool of life carries long-term significance. The UK Baby Biome program research shows that newborn guts are essentially sterile and acquire their microbiome in the first days after birth, an event that helps “train” the immune system for decades to come.
Babies delivered vaginally tend to acquire beneficial gut bacteria such as Bifidobacterium longum from their mother’s intestine, while the guts of those born by Caesarean section are more likely to be colonized initially by hospital-associated bugs. These early differences appear to matter; infants whose guts are dominated by B. longum are roughly half as likely to be hospitalized for respiratory infections in early childhood, and early microbiome patterns have been linked to later risks of allergy, asthma, obesity, inflammatory bowel disease, and even neurodegenerative disease. The mechanism is thought to involve microbial production of fatty acids that shape immune tolerance and gut barrier function. In short, the first bowel movement is not just a developmental milestone, it is the opening entry in a lifelong gastrointestinal flight log. Talking of entries, what did Spock find in the Enterprise toilet…the Captain’s log.
While one can test for blood hidden in the stool by smearing some on a card and sending it to the lab (FOB: fecal occult blood test or FIT: fecal immunochemical test), the throne itself could help diagnose bowel disease as the humble toilet is transformed into a health-monitoring platform. Leading manufacturers are embedding sensors, clever electronics, and artificial intelligence into smart toilets that can analyze stool for indicators of hydration status, gut health, and even traces of blood—saving you from having to smear poop on a piece of cardboard. Tracking information over time with AI interpretation and communicating data securely via smartphone apps could offer insights that might preempt disease. A bathroom with superpowers—one might say Flush Gordon!
Pilots should self-ground when any new condition appears that could impair safe flight. Gastrointestinal red flags that mandate grounding include diarrhea, vomiting, abdominal pain, black or bloody stools, symptoms of dehydration or dizziness, severe or systemic illness, and unexplained weight loss or fatigue. You would not launch with a known system fault; do not attempt takeoff with these symptoms.
Many gastrointestinal conditions must be reported during aeromedical certification, particularly if chronic, recurrent, or requiring ongoing treatment. New diagnoses of inflammatory bowel disease, gastrointestinal bleeding, malabsorption syndromes, pancreatic disease, and cancer should all obviously be disclosed to your AME.
Short-lived issues such as brief constipation or diet-induced diarrhea that fully resolve typically do not require further attention, but transparency is essential. From a certification standpoint, cover-ups cause far more turbulence than diagnoses.
Stool is not polite conversation, but it is critical data. It is the gastrointestinal equivalent of the cockpit voice and flight data recorder—unforgiving, honest, and invaluable after the fact. Pay attention early, act decisively, ground yourself when required, and involve your AME appropriately. Your health, your passengers, and your certificate all depend on it. And as a final note, take a peek at your poop before flushing—it could save your life. And at the risk of causing eye rolls if not aileron rolls, poop jokes aren't my favorites...but they’re a solid No. 2.
Fly Well!
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