Transrectal Ultrasound Measurement of Prostate Compartment Tissue

Pressure in BPHNeil Wasserman, M.D., FACR

University of Minnesota

Aug. 5, 1994

Introduction• There have been no prior reports of

direct measurement of intraprostatic tissue pressure.

Hypothesis• Interstitial prostate tissue pressure

increases with age and development of benign prostatic hyperplasia (BPH) .

• The degree to which patients experience symptoms relates to how the mechanically enlarged prostate manages this pressure.

• Tissue pressure can be measured in vivo.

Materials & Methods I• Patients (n=5)– Referred in 1995 for transrectal ultrasound

(TRUS) guided biopsy for suspicious digital rectal examination (DRE) and/or ⬆ PSA

– No known history of prostatitis or prostate surgery or minimally invasive therapies

• Patient Preparation– Ciprofloxasen 500 mg prior day and morning of

study– Fleet® enema– 2% lidocaine anesthesia

Material & Methods II• Symptom Scoring– International Prostate Symptom Score

(IPSS) self admin. Questionaire• 7 symptoms @ 1-5 points in ascending

severity (total ≤ 35)

Material & Methods III• Prostate Volume Measurement– Prolate ellipsoid geometric model• AP diam. (cm) x Transverse diam. (cm) X

Length (cm) x 0.52

Material & Methods IV• Instrumentation– iU22 ultrasound machine (Philips

Medical Systems, Bothell, WA) using a 12-MHz gray scale, 5-MHz end fire Doppler transducer w/ biplane probe

–Model 420 Camino Laboratories pressure monitor

– 4F fiberoptic catheter with pressure sensor at its tip

Material & Methods V

Material & Methods VI• Placement Techniques– Pressures measured prior to Bx passing

catheter through 15g spinal needle trocar– Measurements made on side without susp. DRE– Trocar passed into target area, transducer tip

catheter inserted to tip, and trocar withdrawn 5 mm to expose pressure transducer to surrounding tissue

Materials & Methods VII• Sites Measured– Extracapsular space (ECS), transition zone (TZ),

peripheral zone (PZ), and central zone (CZ) when identifiable

• Position of tip and pressure stabilized checking for fluctuation with the probe balloon inflated and deflated and per monitor before 2 measurments from each site attempted and recorded

• Transducer calibrated to 0-1 mmHg while within the catheter at the beginning of the examination

Materials & Methods VIII• 2 measurements at each site

attempted – At rest– During Valsalva–With pelvic floor contraction

• Transducer calibrated within catheter at the end of the examination

Results

*

* = mmHg

Results I• Mean Age = 69 yrs. (65-73)• Mean IPSS = 10.2 (5.8-14)• Mean Total Vol. = 82.2 cc (41.2-169)• Mean TZ Vol. = 53 cc (22.5-118)• Mean transducer calibration at exam

end = 1 mmHg (0-2)• No biopsy + cancers

Results II• All intracapsular pressures > ECS• Mean resting pressures were greatest in

the TZ, followed by PZ and CZ• Pressures ⬆ significantly with Valsalva and

to lesser degree with pelvic contraction• 1 patient with largest vol.(169/118) and

pressures showed Type 3 BPH with dominant Retrourethral (median) lobe protruding into the bladder

Discussion I• Type 2 BPH

– Dominant enlargement of the retrourethral lobe (R)– Minimal transition zone extending anteriorally across

midline (T)– Course of urethra (yellow arrows)– Central zone (C)– Course of ejaculatory duct (green arrows)

P

T

C

R

R

v

cNote: Retrourethral lobe is “trapped” under the trigone resulting in high intracapsular pressure

Discussion II• Type 3 BPH– Balanced enlargement of TZ

and Retrourethral lobe

Note early “herniation” of the latter through the bladder neck in an attempt to decompress pressure

P

PT

T

C

R R

Discussion III • Type 1 BPH

– Enlargement of TZ compresses the Peripheral zone reflecting very high intracapsular pressure and elongates the AP axis

P P

TTv

Normal High Pressure BPH

Discussion IV• Sources of Error– Respiratory motion effects intra-abdominal

pressures potentially causing variations in pelvic pressure.

– Operator hand movement holding transducer catheter.

– No accounting for Retrourethral (median lobe) size or adenoma protrusion into bladder base.

– Very small patient sample (n = 5).– Missing values due to technical issues.

Discussion V• Calibration of pressures before,

during, and after measurement attempt to minimize the first two potential sources of error

• All pressure exceeded normal intra-abdominal pressure (<12 mmHg)

Conclusions• The order of magnitude of intra- and extraprostatic

pelvic pressure was established and is surprisingly high in pts. with BPH.

• Compartment pressure is highest in the TZ, less in the PZ and CZ and least in the extraprostatic space.

• All intraprostatic pressures are maximal with Valsalva maneuver and elevated with pelvic muscle contraction compared with resting pressure.

• All pressures exceed normal intra-abdominal pressure measured in other studies in the literature.

Epilogue• Subsequent to this study, tissue

pressure was measured in pts. with prostatitis and found to be of the same order of magnitude as in our patients with BPH.

References• Wasserman NF. Benign Prostatic Hyperplasia: A review and

ultrasound classification. Radiol. Clinics No. Amer 2006; 44:689-710

• Mehik A, Hellstrom P, Lukkarinen O, Sarpola A, Alfthan O. Increased intraprostatic pressure in patients with chronic prostatitis. Urol Res 1999;27:277-279

• McDermott AGP, Marble AE, Eng P, Yabsley RH. Monitoring acute compartment pressures with S.T.I.C. catheter. Clinical Orthopaedics and Related Research 1984;190:192-198