A full medical, psychosexual and psychiatric history should be documented. The physician should explore the patient’s concerns about appearance and body image (ruling out body dysmorphic disorder). Additionally, the physician should inquire about overall beliefs, personal values, and assumptions that the patient is making about his or her genitals. Given that Koro is often an “attack” with a great deal of associated anxiety, the physician should ascertain the patient’s emotional state along with the timeline from onset to the presentation at the examination.

A physical examination should involve an assessment of overall health along with a detailed genital examination. In men, genital examination should be performed immediately after penile exposure, to avoid changes due to external temperature. The primary intent of the male exam is to exclude genuine penile anomalies such as hypospadias, epispadias and Peyronie's disease. The presence of a significant suprapubic fat pad should be noted as well. Careful measurements of flaccid length, stretched length and flaccid girth will also be useful. If male patients insist that their penis is shrinking and disappearing, measurements after intracavernosal alprostadil may be used in the office to determine the true erect length and to diagnose any penile abnormalities in the erect state. A physical examination should note any injuries inflicted by the patient in an effort to "prevent" retraction as further confirmation of Koro.

Several criteria are typically used to make a diagnosis of koro. The primary criteria is a patient's report of genital (typically penile or female nipple) retraction despite a lack of objective physical evidence demonstrating retraction. This is accompanied by severe anxiety related to the retraction, fear of death as a result of retraction, and use of mechanical means to prevent retraction. Cases that do not meet all the requirements are generally classified as koro-like symptoms or given a diagnosis of partial koro syndrome. It has been argued that the criteria are sufficient but not necessary to make a diagnosis of koro. Researchers have identified Koro as a possible "cultural relative" of Body Dysmorphic Disorder. DSM-IV explains the process of differential diagnosis between these two disorders.

Ultrasound examination is able to depict the tunica albuginea tear in the majority of cases (as a hypoechoic discontinuity in the normally echogenic tunica). In a study on 25 patients, Zare Mehrjardi et al. concluded that ultrasound is unable to find the tear just when it is located at the penile base. In their study magnetic resonance imaging (MRI) accurately diagnosed all of the tears (as a discontinuity in the normally low signal tunica on both T1- and T2-weighted sequences). They concluded that ultrasound should be considered as the initial imaging method, and MRI can be helpful in cases that ultrasound does not depict any tear but clinical suspicious for fracture is still high. In the same study, authors investigated accuracy of ultrasound and MRI for determining the tear location (mapping of fracture) in order to performing a tailored surgical repair. MRI was more accurate than ultrasound for this purpose, but ultrasound mapping was well correlated with surgical results in cases the tear was clearly visualized on ultrasound exam.

Priapus, a minor Greek god of fertility, is marked by his oversized, permanent erection, which gave rise to the medical term priapism. Some researchers believe the depiction of Priapus' penis referred to a penile disease, and that paintings of Priapus were used to ward off the disease.

Penile fracture is a medical emergency, and emergency surgical repair is the usual treatment. Delay in seeking treatment increases the complication rate. Non-surgical approaches result in 10–50% complication rates including erectile dysfunction, permanent penile curvature, damage to the urethra and pain during sexual intercourse, while operatively treated patients experience an 11% complication rate.

In some cases, retrograde urethrogram may be performed to rule out concurrent urethral injury.

Most penile trauma can be diagnosed by visual and physical examination, but in some cases, ultrasonography can indicate the extent of the injury and help a clinician decide if the injured person needs surgical treatment.

Aposthia is a rare congenital condition in humans, in which the foreskin of the penis is missing.

Toward the end of the nineteenth century, E. S. Talbot claimed that aposthia among Jews was evidence for the now-discredited Lamarckian theory of evolution. In his work, ""The Variation of Animals and Plants under Domestication"", Charles Darwin also mentioned cases of "born circumcised" babies as "conclusive evidence" for the now-discredited blending inheritance.

It is likely that the cases he described were actually hypospadias, a condition in which the urinary meatus is on the underside of the penis. Neither condition has been shown to have a higher frequency in Jews or Muslims.

Penetrating and blunt traumas combined make up approximately 90% of all civilian penile injuries (45% each), with burns and other accidents making up the remaining 10%.

Formicophilia, a form of zoophilia, is the sexual interest in being crawled upon or nibbled by insects, such as ants, or other small creatures. This paraphilia often involves the application of insects to the genitals, but other areas of the body may also be the focus. The desired effect may be a tickling, stinging or in the case of slugs, slimy sensation, or the infliction of psychological distress on another person. The term was coined by Ratnin Dewaraja and John Money in 1986 from the Latin "formica" (ant) + the Greek "philia" (love).

Penile Revascularization is a specialized vascular-surgical treatment option for Erectile Dysfunction. The 2009 International Consultation on Sexual Dysfunctions recommended that revascularization be limited to nonsmoker, nondiabetic men younger than 55 years of age with isolated stenosis of the internal pudendal artery with absence of venous leak.

Patients with persistent erectile dysfunction after revascularization may benefit from repeat penile duplex ultrasound and pelvic angiography to evalauate the status of the bypass graft and to exclude the presence of a PASS as the cause. The prevalence of an aberrant obturator artery arising from the inferior epigastric artery is approximately 10.5%. If an aberrant obturator artery is visualized arising from the inferior epigastric artery prior to surgical penile revascularization, consideration should be given toward using an alternative source artery or to embolization to avoid the creation of a Penile Artery Shunt Syndrome encountered in this described case.

Diagnosis is made by taking samples for bacterial culture from all accessible sites. In mares, this includes the endometrium, cervix, clitoral fossa and sinuses. In stallions, samples are taken from the skin folds of the prepuce, urethral fossa, urethra, and the pre-ejaculatory fluid. Samples are refrigerated and transported to an approved testing laboratory within 48 hours of collection.

Blood tests for mares are available for detecting antibodies to "Taylorella equigenitalis". Blood tests are not possible for stallions. These tests become positive 10 or more days after infection. If positive, they only indicate that the mare has had the disease in the past, and do not indicate whether the mare is a carrier now.

Percutaneous Coil Embolization of the aberrant obturator artery was performed. Arterial flow rapidly improved through the left dorsal penile artery, and brisk opacification was seen through to the glans penis. Post-procedure, the patient experienced an immediate improvement in erectile function.

The disease is effectively treated with antibiotics, therefore, developed countries have a very low incidence of donovanosis; about 100 cases reported each year in the United States. However, sexual contacts with individuals in endemic regions dramatically increases the risk of contracting the disease. Avoidance of these sexual contacts, and sexually transmitted disease testing before beginning a sexual relationship, are effective preventative measures for donovanosis.

The first known name for this condition was "serpiginous ulcer", which dates to 1882. The proper clinical designation for donovanosis is now "granuloma inguinale". A granuloma is a nodular type of inflammatory reaction, and inguinale refers to the inguinal region, which is commonly involved in this infection. The disease is commonly known as donovanosis, after the Donovan bodies which are a diagnostic sign.

The causative organism, "Klebsiella granulomatis", was called "Calymmatobacterium granulomatis", and some sources still use this classification, from the Greek "kalymma" (a hood or veil), referring to the lesions that contain the bacteria. Prior to this, it was called "Donovania granulomatis", named after the Donovan bodies.

The specific name "granulomatis" refers to the granulomatous lesions. The organism was recently reclassified under the genus "Klebsiella", a drastic taxonomic change since it involved changing the organism's phylum. However, polymerase chain reaction techniques using a colorimetric detection system showed a 99% similarity with other species in the "Klebsiella" genus.

A urologist may be able to diagnose the disease and suggest treatment. An ultrasound can provide conclusive evidence of Peyronie's disease, ruling out congenital curvature or other disorders.

The diagnosis is often based on the history of the condition and the physical exam.

Blood gas testing the blood from the cavernosa of the penis can help in the diagnosis. If the low flow type of priapism is present the blood typically has a low pH while if the high flow type is present the pH is typically normal. Color doppler ultrasound may also help differentiate the two. Testing a person to make sure they do not have a hemoglobinopathy may also be reasonable.

Diagnosis may include careful identification of the cause with the aid of a good patient history, swabs and cultures, and pathological examination of a biopsy.

Distal shunts, such as the Winter's, involve puncturing the glans (the distal part of the penis) into one of the cavernosa, where the old, stagnant blood is held. This causes the blood to leave the penis and return to the circulation. This procedure can be performed by a urologist at the bedside. Winter's shunts are often the first invasive technique used, especially in hematologically induced priapism, as it is relatively simple and repeatable.

Proximal shunts, such as the Quackel's, are more involved and entail operative dissection in the perineum to where the corpora meet the spongiosum, making an incision in both, and suturing both openings together. Shunts created between corpora cavernosa and saphenous vein called Grayhack shunt can be done though this technique is rarely used.

As the complication rates with prolonged priapism are high, early penile prosthesis implantation may be considered. As well as allowing early resumption of sexual activity, early implantation can avoid the formation of dense fibrosis and hence a shortened penis.

Upon delivery, the exposed bladder is irrigated and a non-adherent film is placed to prevent as much contact with the external environment as possible. In the event the child was not born at a medical center with an appropriate exstrophy support team then transfer will likely follow. Upon transfer, or for those infants born at a medical center able to care for bladder exstrophy, imaging may take place in the first few hours of life prior to the child undergoing surgery.

Primary (immediate) closure is indicated only in those patients with a bladder of appropriate size, elasticity, and contractility as those patients are most likely to develop a bladder of adequate capacity after early surgical intervention.

Conditions that are absolute contraindications despite bladder adequacy include duplication of the penis or scrotum and significant bilateral hydronephrosis.

"Taylorella equigenitalis" is susceptible to most antibiotics, although the carrier state in mares is difficult to eliminate. Most mares with acute endometritis recover spontaneously. Recommended therapy is to infuse the uterus with an antibiotic such as penicillin, cleansing the clitoral area with 2% chlorhexidine solution and then applying chlorhexidine or nitrofurazone ointment to the clitoral fossa and sinuses. The entire treatment is repeated daily for five days.

It is relatively easy to eliminate the carrier state in stallions using local disinfectant. With the stallion's penis dropped and the glans extended from the foreskin, the shaft of the penis, including the folds of the prepuce and the urethral fossa, should be cleansed daily for five days with a 2% chlorhexidine solution. After drying, nitrofurazone cream is applied to these areas.

Diphallia, penile duplication (PD), diphallic terata, or diphallasparatus, is a rare developmental abnormality in which a male is born with two penises. The first reported case was by Johannes Jacob Wecker in 1609. Its occurrence is 1 in 5.5 million boys in the United States.

When diphallia is present, it is usually accompanied by renal, vertebral, hindgut, anorectal or other congenital anomalies. There is also a higher risk of spina bifida. Infants born with PD and its related conditions have a higher death rate from various infections associated with their more complex renal or colorectal systems.

It is thought diphallia occurs in the fetus between the 23rd and 25th days of gestation when an injury, chemical stress, or malfunctioning homeobox genes hamper proper function of the caudal cell mass of the fetal mesoderm as the urogenital sinus separates from the genital tubercle and rectum to form the penis.

A ectopic testis is a testicle that, although not an undescended testicle, has taken a non-standard path through the body and ended up in an unusual location.

The positions of the ectopic testis may be: in the lower part of the abdomen, front of thigh, femoral canal, skin of penis or behind the scrotum. The testis is usually developed, and accompanied by an indirect inguinal hernia. It may be divorced from the epididymis which may lie in the scrotum.

The condition may be treated with surgery. There are several different techniques to treat this condition. Threading a suture through the lower membrane, and then tying a tight knot around the frenulum itself is a procedure that minimises invasive action. After a few days the frenulum will weaken and eventually break apart to allow the prepuce to fully retract. Other procedures involve the cutting of the skin and require the use of sutures to help in the healing process. Stretching exercises and steroid creams may also be helpful. Alternatively, it may be treated by a reparative plastic surgery operation called a frenuloplasty, or by complete circumcision including resection of the frenulum (frenectomy).

In a small retrospective study of 25 pregnancies five factors were found to be strongly associated with a prenatal diagnosis of bladder exstrophy:

- Inability to visualize the bladder on ultrasound

- A lower abdominal bulge

- A small penis with anteriorly displaced scrotum

- A low set umbilical insertion

- Abnormal widening of the iliac crests

While a diagnosis of bladder exstrophy was made retrospectively in a majority of pregnancies, in only three cases was a prenatal diagnosis made.

In the first reported case study, the patient had started keeping ants in a cupboard of his room as a hobby when he was nine. At this age he enjoyed "the ticklish feeling" of the ants crawling on his legs and thighs. At age ten, he had a sexual relationship with another boy, and was beaten when his father discovered this. By the age of 13 or 14, he had added snails and cockroaches to his collection, and was becoming increasingly preoccupied with it. He had begun masturbating while the ants crawled on his legs. At age 28, he was masturbating several times a week while cockroaches crawled on his thighs and testicles, and snails crawled over his nipples and penis. Sometimes he would hold a frog against his penis and enjoy the vibrations as it tried to escape. The patient was disgusted by his habit, but derived no pleasure from normal sexual activities. John Money suggested that the paraphilia developed as an alternative outlet after his normal sexual expression became associated with the trauma of his father's punishment.

Another case was described in 2012. At the age of 14, the patient saw an ice-cream stick covered with ants, and wondered how it would feel if his penis was in place of the stick. He began letting ants crawl on his genitals, especially fire ants, a practice he found sexually exciting and that continued into adulthood. The patient was socially and intellectually competent. He was also attracted to dogs and goats.