ACR Appropriateness Criteria®
Clinical Condition: Obstructive Voiding Symptoms Secondary to Prostate Disease
Variant 1: Normal renal function.
| Radiologic Procedure |
Rating |
Comments |
RRL* |
| US bladder transabdominal |
7 |
Post-void to measure residual urine. If there is significant residual, evaluation of upper tracts is indicated. Gives estimate of prostate size. Resistive indices (RI) have been shown to be elevated in BPH and to decrease after transurethral vaporization of the prostate, suggesting that RI can be used to evaluate severity of BPH and monitor therapy. |
None |
| US kidney transabdominal |
3 |
Appropriateness rating could be higher if significant residual urine were present. Evaluate for hydronephrosis. |
None |
| X-ray intravenous urography |
3 |
Appropriateness rating could be higher if significant residual urine is present. In patients with stones, hematuria, or atypical history, the study may be warranted. CT urography has replaced IVU in some centers. |
Low |
| MRI pelvis |
2 |
|
None |
| INV voiding cystourethrography |
2 |
Consider in men younger than 50 with symptoms. |
IP |
| X-ray abdomen |
2 |
Other imaging studies more useful. |
Low |
| US prostate transrectal |
2 |
|
None |
| X-ray retrograde urethrogram |
2 |
Does not assess prostate size. |
Med |
| CT abdomen and pelvis |
1 |
Not indicated. |
High |
| Rating Scale: 1=Least appropriate, 9=Most appropriate |
*Relative Radiation Level |
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Increased blood urea nitrogen (BUN) and/or creatinine. (Refer to ACR Appropriateness Criteria® for Renal Failure. For example, in patients who have elevated renal function tests even after catheter drainage, renal scintigraphy should be considered.)
| Radiologic Procedure |
Rating |
Comments |
RRL* |
| US bladder transabdominal |
8 |
To evaluate for residual urine and prostate size. Resistive indices (RI) have been shown to be elevated in BPH and to decrease after transurethral vaporization of the prostate, suggesting that RI can be used to evaluate severity of BPH and to monitor therapy. |
None |
| US kidney transabdominal |
8 |
To evaluate for hydronephrosis. |
None |
| X-ray abdomen |
3 |
To exclude calculi. Can be used in association with ultrasound. |
Low |
| US prostate transrectal |
2 |
Can assess prostate size by transabdominal ultrasound. |
None |
| X-ray intravenous urography |
2 |
Other studies better for evaluating same structures. |
Low |
| X-ray retrograde urethrogram |
2 |
Does not assess prostate size. |
Med |
| MRI pelvis |
2 |
|
None |
| INV voiding cystourethrography |
2 |
Consider in men younger than 50 with symptoms. |
IP |
| CT abdomen and pelvis |
1 |
Not indicated. |
High |
| Rating Scale: 1=Least appropriate, 9=Most appropriate |
*Relative Radiation Level |
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Summary of Literature Review
Obstructive voiding symptoms secondary to prostate disease include hesitancy, decreased force of stream, terminal dribbling, post-void fullness, and double voiding. Benign prostatic hypertrophy (BPH) is the most common cause of prostate enlargement requiring intervention. It is estimated that by 80 years of age, 75% of men have developed BPH. It has been hypothesized that age related impairment of blood supply to the lower urinary tract is important in the development of BPH. It has also been estimated that 10% of all males older than age 40 will have BPH requiring surgery before reaching age 80. Other causes of bladder outlet obstruction include urethral stricture, prostate cancer, bladder neck contracture, and neurogenic disease.
Numerous imaging studies have been used in evaluating patients with symptoms of bladder outlet obstruction. These include plain films, intravenous pyelography (IVP), urethrography, both transabdominal and transrectal ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI). With the coming re-engineering of health care, selective use of these modalities will be required in order to decrease costs and practice efficient, effective medicine.
Plain-film radiography cannot be used to visualize the prostate directly. A distended bladder can be visualized as a pelvic mass, but unless information is available regarding when the patient last voided, this finding is of uncertain value. Prostatic calcifications can be visualized and always indicate glandular enlargement if they extend above the pubic symphysis. Bladder calculi can also be easily identified. In patients with prostate cancer and bone metastases, plain films are a valuable and inexpensive diagnostic tool. Eighty percent of bone metastases are osteoblastic, and mixed osteoblastic and osteolytic lesions are seen in another 15% of patients. However, bone scintigraphy is far more sensitive in identifying bone metastases at an early stage.
The routine use of IVP is not recommended. In patients who have stones on plain films, hematuria, or an atypical history, however, IVP may be warranted. There is no evidence that patients with BPH have a higher incidence of asymptomatic renal cancers than the general population in the same age group; therefore, an IVP to search for occult neoplasms is unwarranted. In a prospective study of 502 patients, the researchers found benign renal cysts in 10%, renal cancers in less than 1%, and significant upper urinary tract obstruction in 2.6%. When patients have obstructive symptoms and renal insufficiency, ultrasound (US) rather than IVP is recommended to evaluate for hydronephrosis. In patients with severe hydronephrosis, azotemia is almost always present, and US is indicated. In summary, while not routinely recommended, upper urinary tract imaging is indicated in patients with BPH and either hematuria (including asymptomatic microscopic), laboratory evidence of renal insufficiency, history of urinary tract infection, urolithiasis, previous urinary tract surgery, or congenital or acquired renal disease.
Retrograde urethrography is valuable to exclude urethral strictures but does not accurately assess the size of the prostate gland. As such, it is not part of the routine evaluation of patients with prostatism. Voiding cystourethrography should be considered only for men younger than age 50 with outflow obstruction symptoms.
Sonography can be used to evaluate the prostate transabdominally (through a distended bladder) or transrectally (TRUS). TRUS is preferred by urologists. The US pattern is still too nonspecific to differentiate benign from malignant prostate lesions. A particular problem is the difficulty in identifying isoechoic lesions. Recently the use of resistive index (RI) in prostate disease has been proposed as helpful. RI has been found to be elevated in the transition zone of patients with BPH, but not in the peripheral or central zones and not in normal patients or those with prostate cancer. RI has also been shown to decrease after transurethral vaporization of the prostate, suggesting that RI can be used to evaluate severity of BPH and monitor the outcomes of therapy. TRUS is, however, used to guide lesion-directed and systematic biopsies of the prostate. It has been suggested that US contrast agents will make tumors more conspicuous, thus improving the detection rate of malignancy in contrast-enhanced targeted cases compared to sextant cases. Three-dimensional (3D) US may prove to be of value in the future.
Secondary changes of bladder outlet obstruction, such as bladder wall thickening, are better seen with US than IVP. The size of the enlarged prostate can be detected accurately by TRUS and MRI, but inaccuracies arise when using transabdominal US. TRUS and MR imaging have an advantage in that the internal prostatic anatomy is better seen and the ratio of glandular to stromal tissue in the prostate can be determined, although to date this information has not proven clinically useful. Identifying the size of the prostate is important since it helps determine the type of therapy indicated. Abdominal (suprapubic) US may be used to accurately (plus or minus 15%) measure residual urine volume in 90% of patients. However, catheterization is probably the least expensive method to accurately assess residual urine in the bladder.
In patients with azotemia, the collecting system of the kidneys should be imaged for dilatation. In patients with normal renal function, this may not be necessary. However, in a study of 128 patients, one group of researchers reported that hydronephrosis can be present with normal biochemical results.
The Clinical Practice Guideline of the Agency for Health Care Policy and Research (AHCPR) states that imaging of the upper urinary tracts by US or IVP is "not recommended unless patients have one or more of the following: hematuria, urinary tract infection, renal insufficiency (excluding IVP), history of urolithiasis, or history of urinary tract surgery".
CT has not proven to be of much value in evaluating the benign, enlarged prostate. There are reports of the value of MRI in evaluating the prostate gland. MRI is also useful in evaluating prostate size, although other less costly procedures, such as US, are preferred.
In summary, in patients who have normal renal function but suffer the symptoms of prostatism, a radiographic workup should be minimal. US is occasionally desirable for estimating prostate size prior to surgery. If azotemia is present, the upper urinary tracts should definitely be evaluated with US for the presence of hydronephrosis.
Abbreviations
- BPH, benign prostatic hypertrophy
- CT, computed tomography
- IP, in progress
- INV, invasive
- IVU, intravenous urography
- Med, medium
- MRI, magnetic resonance imaging
- RI, resistive index
- US, ultrasound
