Two daughters bring their severely demented mother into the clinic. The mother is no longer able to speak, but over the last few days she has groaned more during diaper changes. Her nursing home is worried she might have a bladder or vaginal infection. To check her urine, we undress her and catheterize her. To check her vagina, we take a swab using a speculum. We spin the urine and look for sediment under the microscope. Nothing. We look at the vaginal smear under the microscope, using both a saline prep and potassium hydroxide. Nothing. We treat her for bacterial vaginosis, because it's a condition that's easy to miss.
A week later, the daughters bring their mother back. Once again we are thorough. Once again we are stumped. Once again we trust the daughters that the groans are worse. We take a careful history. We think of all the possible bad things. The worst things. But this nursing home is a good place. The caregivers there are experienced, well-liked, kind-hearted and trustworthy. This time we treat her for a possible yeast infection.
A week later, the daughters bring their mother back yet again. Same drill. Same result. Maybe some topical estrogen? The clinic nurses have her dressed again and ready for the ambulance ride back to the nursing home, when suddenly it's clear her diaper has been soiled. I'm walking by and lend a hand. We slide the old diaper off, cleanse her in front, roll her over to clean her from behind--and spot what's left of shingles sneaking into her gluteal crease and plunging deep into her nether regions.
"That's the S3 dermatome," I tell the resident--the skin area supplied by one of the spine's sacral nerves. "Add that to your differential," I tell the resident--a reminder to look everywhere in considering the diagnostic possibilities. "Don't miss a chance to help clean a naked patient," I tell anyone who will listen.