Anejaculation is the pathological

Pathology

Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

 inability to ejaculate

Ejaculation

Ejaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...

 in male

Male

Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...

s, with (orgasmic) or without (anorgasmic) orgasm.
It can depend on one or more of several causes

Etiology

Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....

, including (ordered by frequency)':

• Sexual inhibition
  Sexual inhibition
  A sexual inhibition is a conscious or unconscious constraint or curtailment by a person of behaviour relating to specific sexual matters or practices or of a discussion of sexual matters....
  
  
• Pharmacological
  Medication
  A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
  
   inhibition
  Reaction inhibitor
  A reaction inhibitor is a substance that decreases the rate of, or prevents, a chemical reaction.-Inhibition of a catalyst:An inhibitor can reduce the effectiveness of a catalyst in a catalysed reaction...
  
  
• Autonomic nervous system
  Autonomic nervous system
  The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
  
   malfunction
  Malfunction
  A malfunction is when something functions wrongly or does not function at all.Some types of malfunctions are:*Malfunction , malfunction of a parachute*Sexual malfunction, also called "sexual dysfunction"**See also dyspareunia...
  
  
• Prostatectomy
  Prostatectomy
  A prostatectomy is the surgical removal of all or part of the prostate gland. Abnormalities of the prostate, such as a tumour, or if the gland itself becomes enlarged for any reason, can restrict the normal flow of urine along the urethra....
  
   - surgical removal of the prostate.
• Ejaculatory duct obstruction
  Ejaculatory duct obstruction
  Ejaculatory duct obstruction is a congenital or acquired pathological condition which is characterized by the obstruction of one or both ejaculatory ducts. Thus, the efflux of semen is not possible....
  
  

Anejaculation, especially the orgasmic variant, is usually indistinguishable from retrograde ejaculation

Retrograde ejaculation

In the human male reproductive system, retrograde ejaculation occurs when semen, which would normally be ejaculated via the urethra, is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation forcing the semen to exit via the urethra, the path of least...

. However, a negative urinalysis

Urinalysis

A urinalysis , also known as Routine and Microscopy , is an array of tests performed on urine, and one of the most common methods of medical diagnosis...

 measuring no abnormal presence of spermatozoa

Spermatozoon

A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

 in the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 will eliminate a retrograde ejaculation diagnosis.
Thus, if the affected man has the sensations and involuntary muscle-contractions of an orgasm

Orgasm

Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...

 but no or very low-volume semen

Semen

Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

, ejaculatory duct obstruction

Ejaculatory duct obstruction

Ejaculatory duct obstruction is a congenital or acquired pathological condition which is characterized by the obstruction of one or both ejaculatory ducts. Thus, the efflux of semen is not possible....

is another possible underlying pathology of anejaculation.