Interstim, Urodynamics, and Anorectal Manometry: How They Fit Together

Posted by Clark Love on Mar 23, 2017 3:01:20 PM

Urodynamics, Anorectal Manometry, and Interstim - See how they fit togetherUrodynamics are a series of tests that measure the functionality of the lower urinary tract. Urodynamics testing1 may be ordered for a number of symptoms, including pain, incontinence, and changes in a patient’s normal urinary or fecal routine. 

Common urodynamics tests include:

  • Uroflowmetry measures how quickly a patient empties his or her bladder naturally.
  • Pressure uroflowmetry measures the rate of urine voiding while also determining bladder and rectal pressures.
  • Post-void residual volume tests assess the volume of urine that remains in the bladder after voiding.
  • Multichannel cystometry is used to measure the pressure in the rectum and bladder via two pressure catheters. This test is also used for measuring contractions of the bladder wall, as well as the strength of the urethra.
  • Electromyography determines electoral activity in the bladder neck.
  • Urethral pressure profilometry measures strength of sphincter contractions.
  • Fluoroscopy is a moving video x-ray of bladder and bladder neck while the patient voids his or her bladder.

Each test plays an integral role in determining factors such as bladder outlet obstruction, the cause of stress urinary incontinence, pelvic organ prolapse, and other disorders.

What is Anorectal Manometry?

Anorectal manometry2 is a test that determines how the rectum and anal sphincter are functioning. The rectum’s sensitivity, strength, and functionality are all measured.

A catheter is inserted into the anus, beyond the anal sphincter, and into the rectum. A balloon positioned at the tip of the catheter is inflated. As the balloon inflates, contractions in the nerves and muscles in the rectum are recorded.

Anorectal manometry is performed in patients who are experiencing fecal incontinence and constipation. This test is used to determine whether weak anal sphincter muscles or low rectum sensitivity are to blame for fecal incontinence. For constipation, anorectal manometry can determine if the anal sphincter muscles are underperforming. Additionally, this procedure measures whether anal sphincter muscles properly relax, as abnormal sphincter function can cause bowel obstruction.  

What is InterStim?

InterStim is a sacral neuromodulation product that can be used to treat urinary and fecal incontinence, as well as pain relief. Certain forms of urinary or bowel incontinence are caused by miscommunication between the brain and sacral nerves. The InterStim system delivers electronic pulses to the pelvic floor, lower urinary tract, urinary and anal sphincters, and the colon to modulate the activity of these organs.

The InterStim3 product is surgically placed in the patient’s upper buttocks. An electrical lead is implanted on a sacral nerve and a neurostimulator delivers an electrical pulse to the nerve. The patient wears a device, called a programmer, which controls the electrical pulses delivered to the neurostimulator.  

Many patients experience reduced fecal and urinary accidents after implantation of an InterStim device, and others become entirely continent. For some patients, symptoms may worsen.  

How do Interstim, Urodynamics, and Anorectal Manometry Fit Together?

A patient that is presenting for symptoms such as urinary or fecal incontinence will first undergo urodynamics assessment, as well as anorectal manometry if fecal incontinence or constipation is experienced.

Urodynamics testing can rule out other causes of constipation or incontinence, such as pelvic organ prolapse or nerve overactivity. To determine whether an InterStim implant is the right course of action for a patient’s needs, one or both of these tests must be performed to determine the underlying cause of the patient’s problems.

Ultimately, Interstim, urodynamics, and anorectal manometry go hand in hand. A patient that is experiencing symptoms in the lower urinary tract or bowels should first be examined via urodynamics testing and/or anorectal manometry to determine the cause of the disorder. If the patient’s symptoms cannot be controlled via changes in lifestyle or diet, sacral neuromodulation might be the best option.

A short term, less invasive trial is performed to determine the suitability of the procedure. If successful, an InterStim is then permanently placed in the patient’s body for symptom control. During initial studies, 120 patients who recorded an average of 9 or more episodes of fecal incontinence per week had the InterStim device inserted. After 12 months, 88 participants reported a 50% reduction in incontinence, while 43 of those participants became fully continent.

If you want to include both Urodynamics and/or Anorectal Manometry in your practice, click the button below to see how to do it with no upfront investment.  

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  1. Vignoli, G. (2016). Urodynamic Testing: When and Which. Urodynamics, 49-52. doi:10.1007/978-3-319-33760-9_4 Link
  2. Pucciani, F. (2015). Anorectal Manometry. Coloproctology, 1-7. doi:10.1007/978-3-319-10154-5_23-1 Link
  3. Peeren, F., Hoebeke, P., & Everaert, K. (2005). Sacral nerve stimulation: Interstim®therapy. Expert Review of Medical Devices, 2(3), 253-258. doi:10.1586/17434440.2.3.253 Link
  4. Wexner SD, Coller JA, Devroede G, Hull T, McCallum R, Chan M, Ayscue JM, Shobeiri AS, Margolin D, England M, et al. Sacral nerve stimulation for fecal incontinence: results of a 120-patient prospective multicenter study. Ann Surg. 2010;251:441–449 Link

Topics: Anorectal Manometry, urodynamics, InterStim

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