In an early article from 1971, an American urologist raised the subject of circumcision, when commenting on the famous David (Figure 1). David represents an uncircumcised young man, and the discussion elaborates on whether Michelangelo's decision to portray his subject in all his intact nature may have been influenced by local church leaders at the time; that is, a circumcised David might have been politically incorrect¹. Other urologists promptly joined in the discussion, suggesting alternative explanations—such as a joke by the artist², or an alleged lack of interest in precise anatomical detail. Support for this latter argument came from a different commentary, pointing to the presence of blood-filled arm veins in the crucified Christ in the statue Pieta; seemingly Michelangelo was unaware of the existence of venous valves³.

With regard to circumcision, however, the true explanation is probably much simpler: although circumcision was widely practised, in renaissance art it was customary not to admit to the effects of the operation. This is most obvious in the numerous contemporary representations of the Christ Child, who is never shown as circumcised⁴ although circumcision was mandatory in Judaism. Further discussion about the anatomical accuracy of Michelangelo's sculptures has arisen also with regard to his statues Notte and Aurora, two of the four Phases of the day in the Medici family tombs in Florence. In the statue Notte (Figure 2) the shape of the breasts is perceived to be unnatural⁵, and possible explanations are that Michelangelo was unfamiliar with the female body⁶ or that he based the sculpture on a male model with subsequent addition of female-sized breasts⁷; others have remarked that the figure's thighs, neck and shoulders are more male than female. Ensuing commentaries included the adventurous explanation that Michelangelo, reputed to have been homosexual, resented female features and deliberately created a male with added breasts⁸. However, a more recent interpretation offers a morbid explanation—namely, that the left breast has features of locally advanced cancer.

The notion that Michelangelo was ignorant of female anatomy is not convincing. He started dissecting human bodies when aged 18, and many of these dissections took place in the Monastery of Santo Spirito in Florence where the corpses often originated from associated hospitals¹⁰. It is therefore likely that Michelangelo was familiar not only with the anatomy of the female body but also with its pathology. Of interest is also the fact that an almost identical appearance of the breast to the one discussed in the statue Notte can be seen in The Flood, a scene in the frescos of the Sistine Chapel in the Vatican, painted around 20 years before creation of the statue Notte.

An American renal physician reckoned to have found convincing evidence that Michelangelo was familiar with the anatomy and function of the kidneys¹¹. According to Eknoyan, the artist's interest in the kidney started when he became afflicted with urolithiasis and sought help from the most prominent physician in Rome, Realdo Colombo¹². In the painting The Separation of Land and Water on the ceiling of the Sistine Chapel, the mantle of the creator resembles a bisected right kidney¹¹ (Figure 3); furthermore, use of this shape in a painting that represents the separation of land and water strongly suggested to Eknoyan that Michelangelo was well aware of the anatomy and function of the kidney (as understood at the time). In a letter to his nephew in which he complains about recurrent joint pains, Michelangelo mentions that he has been diagnosed as having gout¹³. Nephrologists, of course, may be especially apt to see kidney shapes. Similarly neurologists: previously an American neuroanatomist had noted that, in Michelangelo's fresco the Creation of Adam, also in the Sistine Chapel, the image surrounding God and the angels had the shape of a human brain¹⁴ (see Figure 3). According to Meshberger this was an encoded message from Michelangelo, signifying a belief that the ‘divine part’ humans receive from God is the intellect, and not life—an interpretation strengthened, in his opinion, by the fact that Adam, moments before his creation, is already alive, with his eyes open and completely formed.

A digression from the theme of medicine in Michelangelo's art concerns the artist's own knee, which according to Espinel¹⁵ is depicted in a fresco by Raphael. The painting in the Vatican, commissioned by Pope Julius II at a time when Michelangelo was on site completing the ceiling of the Sistine Chapel, shows an individual with an enlarged and deformed right knee. The figure is in contemporary clothes and not, like others in the picture, in more classical dress. The lumps on the knee are interpreted as gouty tophi, in accordance with the artist's purported diagnosis. However, the notion that this person must be Michelangelo was soon refuted¹⁶.