Biological organisms often produce a variety of mineralized tissues, such as bones, teeth and shells. In addition to those usually produce, individual organisms often produce other biomineralized tissues pathologically, that is due to disease or environmental stress. In human beings such tissues can include gallstones, bladder stones, dental calculus (plaque) or calcified tumours as well as other tissues becoming calcified or ossified.
In a paper published in the journal PLoS One on 2 October 2014, Judyta Gładykowska-Rzeczycka of Gdańsk in Poland and Dariusz Nowakowski of the Department of Anthropology at the Wrocław University of Environmental and LifeSciences describe a pathological ‘stone’ from a medieval burial in Gdansk, Poland.
The site of the burial lies within a graveyard used from the 10th century until 1813, but built over by a church, a monastery and the Market Hall of Gdańsk Old Town. Many of the bodies at the site have been dug up then reburied, resulting in widespread damage to remains, as well as disarticulation and mixing of skeletons. Despite this the site has yielded about 1000 burials, and is under ongoing investigation by the Gdańsk Archaeological Museum.
The stone was recovered from a grave containing four bodies; a man between 40 and 44 years of age, a woman aged 20-39, a teenager of unknown sex and a foetus, dating from the mid tenth to mid fourteenth centuries, and could potentially have come from any of the three older bodies. It is about 39 mm long, 14 mm thick and 12.5 mm deep and weighs 6.87 grams.
A macroscopic view of the stone. Gładykowska-Rzeczycka & Nowakowski (2014).
When cut into transverse sections the stone was found to be made up of concentric layers of clear yellowish material. Chemical analysis revealed this to be composed of calcium carbonate (CaCO3), calcium phosphate (Ca3(PO4)2) and calcium oxalate (CaC2O4), with the proportions of each mineral varying from layer to layer.
Localization of chemical analysis points on transverse section of the stone and concentric layers ofthe stone. Gładykowska-Rzeczycka & Nowakowski (2014).
The absence of any pathology on the skeletons found in the same grave as the stone and absence of venation on the surface of the stone suggest that it is unlikely the stone formed as the result of tissue calcification. The visible layering within the stone suggests that it built up over time, probably with distinct growth phases representing distinct periods of infection or environmental stress. Such stones are typically formed within the kidneys or urinary tract, with the size and concentric layers seem within the stone strongly suggesting that it formed in the bladder. A 39 mm bladder stone is large, but not totally exceptional; stones in excess of 7 cm have been recorded.
Calcium phosphate urinary stones are typically associated with alkaline urine, which in turn is often caused by an infection of anaerobic bacteria, combined with a high phosphate diet, probably containing a lot of fish. Urinary tract stones are most common in societies where little meat or dairy produce are consumed, and where plant matter forms a high proportion of the food intake.
Gładykowska-Rzeczycka & Nowakowski suggest that the large size of the stone implies repeated periods of poor health, probably including periods of starvation or disease, which led to bacterial infection of the kidneys. The exterior of the stone has a rough, porous surface, which may indicate an aggressive bacterial infection during the final phase of stone formation, and was probably also responsible for the death of the person with the stone.
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