Tales Selected from the K-Files

by Dick Gibson

Back to the Kidney Stone Mineralogy page

After analyzing 20,000 kidney stones, you can be sure that there are some stories to tell. Here are a few -- but be warned! If you are the least bit squeamish, go no further!

"The specimen was not of urinary origin."
Foreign Body Nuclei

"The specimen was not of urinary origin." With those simple words our mineralogical reports summarized some strange things. You never knew what you would find when you opened the little yellow pill box most stones were submitted in -- ranging from gold to dead flies and rocks of diverse sorts. We learned that sometimes such findings were offered by patients in order to get drugs, such as the case of the specimen that was a half-inch chunk of cement block, complete with silver paint on one side. We thought that the silver paint seemed rather industrial or institutional, and indeed the doctor wrote back to say that the patient was from a prison.

We never did find out where the gold came from, but there it was, seven little nuggets of soft, porous gold. We presumed it was dental gold, and it was so little that it was not worth even $5, but it was quite a shock to discover it!

The first non-urinary stone arrived while I was still a geology grad student at Indiana University. A quarter-inch long, non-descript, rounded brown pebble-like stone defied identification until it was submitted to x-ray diffraction analysis. This technique reveals crystal structures, which are nearly unique patterns that are characteristic of each mineral, no matter what its origin. The analysis was clear: We had a piece of gehlenite. What is gehlenite? None of my geological colleagues knew either, but the mineralogy texts quickly showed it to be a high-temperature (we're talking hundreds of degrees!) metamorphic mineral, an iron silicate, common in slag piles of steel mills. Sure enough, the specimen had come from a doctor in Cleveland, Ohio, part of the steel belt. We never got any further information about that one, but it may have been a simple mistake in collecting a relatively tiny specimen.

Foreign Body Nuclei Lots of genuine urinary stones nucleate on foreign bodies. These range from the fist-sized stone deposited on a large (2"+) swatch of gauze, to small stones that were crystallized concentrically upon threads and knots of suture material. When I was analyzing stones, in the early 1970's, before the word "malpractice" became common, I saw about 500 stones per month, and approximately one per month had a non-urinary nucleus. The first one came as a shock. The stone was large, more than an inch long and about a half inch across, reminiscent of an irregular white grubworm. It was an aggregation of radiating struvite crystals. The analytical routine called for visual examination of the exterior, then similar study of the interior, so that the initial deposit, or nucleus, could be identified. That nucleus might be more important in a treatment program than the more voluminous outer mineral coatings. To get to the interior, I had a little hammer that broke most stones with a gentle tap. This time, however, the big stone did not break -- the hammer bounced back! More aggressive tapping soon chipped the surficial crystals away to reveal a three-quarter inch length of rubber tubing, completely encased in crystalline struvite and apatite. Various pieces of rubber were the most common foreign body nuclei I saw.

That's it for now! Stay tuned!

Richard I. Gibson, Gibson Consulting - 301 North Crystal St. - Butte, Montana 59701 - Phone/Fax: 406-723-9639 - E-mail