Residual Urine Determination: Treatment, Effect & Risks

Residual urine determination is an examination method used in urology. The aim of this examination is to diagnose a bladder emptying disorder and, if necessary, to determine the cause.

What is residual urine determination?

Residual urine determination is performed in the field of urology to diagnose a possible bladder voiding disorder. Residual urine determination is performed in the field of urology to diagnose a possible bladder emptying disorder. Residual urine is the term used to describe the remaining urine in the bladder after a voluntary urination. The formation of residual urine is often an indication of bladder dysfunction and occurs as an accompanying symptom. The fact that the bladder can only be emptied incompletely is often not noticed by the patient. This only becomes apparent during the course of the disease in the form of a recurring feeling of fullness and a frequent urge to urinate. Residual urine formation often occurs when the bladder is not under tension. Even if the symptoms do not cause any discomfort at first, it is imperative to determine the cause and then to treat it adequately. Without treatment, the risk of urinary tract infection increases enormously and can lead to irreversible damage. To determine the amount of residual urine, an examination is performed using sonography or a bladder catheter. Residual urine of 100 ml counts as pathological in an adult and from about 10 percent of bladder capacity in children. Residual urine forms a potential breeding ground for pathogens and bacteria. Therefore, the risk of recurrent urinary tract infections and the formation of bladder stones is increased. This is manifested by painful bladder emptying, fever, and possibly chills. The residual urine can back up into the kidneys and cause irreversible damage, even acute kidney failure. Often, this also results in a very painful overdistension of the bladder. The urine can no longer be drained, a so-called complete urinary blockage occurs.

Function, effect and goals

There are many causes for the formation of residual urine. These can be, for example, pathological changes in the urethra or penis. Diseases in the area can be phimosis (narrowing of the foreskin), urethral stricture, injuries to the urethra, or urethral carcinoma. Neurological conditions, such as a stroke, multiple sclerosis (MS), paraplegia or a herniated disc can also be responsible for residual urine formation. Occasionally, a traumatic pelvic floor fracture or side effects of antidepressants and antihistamines can also be triggers. Especially in the male gender, prostate enlargement (benign prostatic hyperplasia) or prostate carcinoma can be causative for the formation of residual urine. The enlarged prostate or the proliferation of a carcinoma can lead to a narrowing of the urethra and thus influence or even block the outflow of urine. Especially in females, a lowered uterus can lead to residual urine formation. The lowered uterus can compress the urethra and thus interfere with or block the flow of urine. In the first stage of residual urine formation, the affected person first observes a frequent urge to urinate with the release of small amounts of urine, which is not painful. The bladder cannot be emptied completely and residual urine remains inside the bladder. In order to determine whether this is a pathological urinary behavior, a residual urine determination must be performed. This determination can be performed sonographically (using an ultrasound probe) or through a bladder catheter. In sonographic residual urine determination, a distinction is made between transabdominal sonography (above the abdominal wall) and transvaginal sonography (through the vaginal entrance). In practice, transabdominal sonography is used more frequently. In this case, the patient must go to the toilet and empty his bladder before the sonography. This should be done without pushing, if possible. The patient then lies back on the examination couch and exposes the lower abdomen. Using a lubricant and the ultrasound probe, the retained urine within the bladder can now be calculated through the abdominal wall and assessed by imaging. Alternatively, the ultrasound probe can also be inserted through the vagina with lubricant gel.Determination through a bladder catheter is distinguished between the transurethral bladder catheter and the suprapubic bladder catheter. The transurethral catheter is placed through the urethra into the urinary bladder. In this case, a so-called disposable catheter is used. With the suprapubic catheter, the catheter is inserted into the urinary bladder through the abdominal wall. In this procedure, too, the patient must first empty his bladder without pressing. A disposable catheter is then inserted into the bladder through the urethra and the residual urine is collected in a collection bag to determine the amount. The residual urine determination is called positive if a residual urine of more than 100 ml remains in adults and more than 10% of the bladder capacity in children.

Risks, side effects, and hazards

If residual urine remains in the bladder, bacteria and viruses form in it and become attached to the inner wall of the bladder. As a result, the bladder is not flushed regularly and recurrent bladder infections occur. If the bladder emptying disorder is not corrected, the bacteria and viruses can travel up to the kidneys and cause renal pelvic inflammation. This results in severe pain and possibly irreversible damage to the kidneys. In addition, urinary retention may occur. The kidney drainage system is disturbed in its function because the bladder does not have sufficient capacity to collect further urine. If a backlog occurs within the kidney, this can lead to tissue damage. Furthermore, overdistension of the urinary bladder or a reflexively hypotonic bladder muscle may occur. To prevent irreversible damage to the urinary bladder and kidneys, residual urination should be performed and the causes adequately treated.