Thomas Jefferson's exact cause of death has never been conclusively determined. He wrote in January 1826,
[As to] the state of my health ... it is now 3. weeks since a re-ascerbation of my painful complaint [a severe attack of diarrhea and difficulty urinating] has confined me to the house and indeed to my couch. required to be constantly recumbent I write slowly and with difficulty. yesterday for the 1st time I was able to leave the house and to resume a posture which enables me to begin to answer the letters which have been accumulating.1
Jefferson lived to the ripe old age of 83, but his health had been declining since 1818, when he visited Warm Springs, Virginia, to find relief for his rheumatism in the mineral baths. By some means, he contracted a nasty infection on his buttocks.2 This boil on his "seat" was probably more than furunculosis. Dr. Gordon Jones thinks it likely Jefferson developed a true septicemia, which would explain Jefferson's subsequent "prostration."3 Heavy doses of sulphur and mercury in ointment form helped clear the infection but were debilitating in themselves. Dr. Jones believes the mercury poisoning helped to exacerbate Jefferson's chronic bowel problems in his last years. Other ailments included swollen legs, painful joints, fatigue, a fractured left wrist, a boil on his jaw, increasing deafness, and unspecified illnesses (of two or three weeks' duration) in 1823 and 1824.4 At the same time, Jefferson's mind remained as agile as always, and he took daily rides on horseback. Visitors were impressed by his physical stamina.
But a serious problem manifested itself in 1825. In late July, Jefferson complained to James Monroe that he was experiencing "a difficulty of making water."5 Robley Dunglison was called in and discovered Jefferson had "prostatic hypertrophy of enough degree to obstruct the flow of urine and cause great pain from urinary retention."6 To treat his patient, Dunglison prescribed "bougies," flexible cylinders, made of elastic gum, variable in size, which were introduced through the urethra past the obstruction. Jefferson found relief for his immediate problem. However, in the days before sterile techniques were available, bacteria were invariably introduced. Thus Dr. Jones feels that a pyelitis was bound to occur, damaging the kidneys themselves.7 From this point, Jefferson gradually grew worse, with only occasional periods of good health.
Though Jefferson's diarrhea abated for a spell early in 1826, it returned in full force later in the spring. By June 26, Jefferson was bed-ridden. From July 2 on, Jefferson was largely stuporous, only occasionally rousing to recognize his physician, Robley Dunglison, and his family.
What finally killed him? It was undoubtedly a combination of ailments: exhaustion from intense diarrhea, toxemia from a kidney infection, uremia from kidney damage, and finally orthostatic old-age pneumonia. He might have lived longer under modern medical care, but likely not much longer if his fundamental problem was a late diagnosed prostatic cancer.8