Ultrasonography in the Detection of Residual Urine - Diabetes

Ultrasonography in the Detection
of Residual Urine
KENNETH PITERS, STUART LAPIN, AND ALICE N. BESSMAN
SUMMARY
Eleven patients with distended urinary bladders (10
diabetics with autonomic neuropathy and one patient
with prostatic hypertrophy) were examined by
ultrasonography in an attempt to define the volumes
detectable by this technique. Incremental volumes of
saline were instilled through indwelling Foley catheters
with ultrasonographic examination at each volume.
The ultrasonograms obtained were presented to two
radiologists trained in ultrasonography, who were
asked to identify the presence of residual urine.
There was 97% certainty of recognizing the presence
of 100-cc residual volumes and 100% certainty of
recognizing 150-cc residual volumes. It is concluded
that residual urine volumes greater than 100 cc are
clinically detectable by ultrasonography, a noninvasive
alternative for diagnosing this common diabetic
condition. DIABETES 28:320-323, April 1979.
Because of the noninvasive nature of ultrasonography,
its ability to delineate anatomic
structures has found everincreasing application
in clinical medicine. Cystic structures, such as
pancreatic, 1 thyroid, 2 renal, 3 and hepatic cysts, 4 as well as
the dilated biliary tree 5 are some of the many structures now
being defined.
In the present study we reinvestigated the ability of
ultrasonography to outline the distended urinary bladder of
the diabetic patient with autonomic neuropathy. The desirability
for making the diagnosis of a neurogenic
bladder containing a residual urine arises repeatedly
in diabetology. In the past this diagnosis was made by
one of two invasive techniques: postvoid catheterization
with determination of residual urine volume or intravenous
pyelogram with documentation of the presence of residual
dye on the postvoid radiograph. Prior studies have shown
that ultrasound is poor at quantifying smaller bladder
volumes while retaining usefulness for the qualitative
identification of larger residuals. 6 - 7 We set out to try to
define residual volume that is clinically detectable with
reliability.
METHODS
Patients selected for study were diabetics in whom a diagnosis
of neurogenic bladder had already been established
and in whom the treatment program dictated insertion of an
indwelling catheter. The amount of urine obtained on initial
catheterization was recorded (initial volume). The procedure
for obtaining ultrasound determinations was as follows: The
bladder was allowed to drain by gravity through the
indwelling catheter. Final drainage was effected by syringe
suction applied to the catheter. Using sterile technique,
normal saline was instilled into the bladder at 50 cc increments
up to the initial volume drained at catheterization,
or, to a maximum of 300 cc, whichever was smaller.
At each volume, ultrasound was performed in both longitudinal
and transversal planes at the largest diameter.
At the termination of the study the bladder was reemptied,
and volumes in excess of the amount of fluid
instilled were considered as urine output during the procedure.
This calculated urine output was appropriately
added to the instilled volumes.
The most representative views at each volume were
selected and presented to two radiologists trained in the
field of ultrasonography. Neither radiologist was given any
diagnostic information. Each was asked to identify fluid
within the urinary bladder. Replies were tabulated as either
correct or incorrect as compared with the known volumes.
Group A represented empty bladders; group B, 50 cc; group
C, 100 cc; and group D, 150 cc.
RESULTS
Twelve patients were studied—eight women and four men.
The mean age was 56 (range, 22-91). All patients were
diabetic: eleven had neurogenic bladders and one man had
benign, prostatic hypertrophy with obstructive urinary
retention.
Table 1 summarizes the data regarding correct and in-
320 DIABETES, VOL 28, APRIL 1979

FIGURE 1. Sagittal echograms of urinary bladder; top—50-cc volume; bottom—100-cc volume. W, abdominal wall; B,
urinary bladder.
DIABETES, VOL. 28, APRIL 1979 321

iz.-
FIGURE 2. Transversal (top) and sagittal (bottom) echograms of urinary bladder in patient with enlarged prostate. Bladder
volume, 150 cc. W, abdominal wall; B, urinary bladder; F, Foley balloon (5-cc volume); P, prostate gland.
322 DIABETES, VOL. 28, APRIL 1979

K. PITERS, S. LAPIN, AND A. N. BESSMAN
TABLE 1
Results of ultrasonography evaluation
Group
Vol
Projection*
No. of
samples
No. of
replies
No.
correct
No.
incorrect
%
correct
A
A
A
B
B
B
C
C
C
D
D
D
0
0
0
50
50
50
100
100
100
150
150
150
T
S
Tand S
T
S
T and S
T
S
T and S
T
S
T and S
16
13
29
17
17
34
19
11
30
12
13
25
32
26
58
34
34
68
38
22
60
24
26
50
25
16
41
26
29
55
37
21
58
24
26
50
7
10
17
8
5
13
1
1
2
0
0
0
78
62
71
77
86
81
97
95
97
100
100
100
* T = Transversal; S = Sagittal.
Marked irregularities of the shape of the bladder were noted. These irregularities were more pronounced in the sagittal views
than in the transversal views. In the sagittal view the inferior margins tended to be indistinct and the posterior margins appeared irregular.
correct interpretations of the presence or absence of visible
fluid in the bladder. The appropriate volumes are listed.
Figure 1 contains echograms of a patient, clearly demonstrating
an echo-free space corresponding to 50 cc and
100 cc volumes, respectively. Figure 2 is echograms of a
patient in two different planes, demonstrating an echo-free
space corresponding to 150 cc volume; in this figure,
both the Foley catheter balloon (5 cc volume) and the
enlarged prostate can be seen. On the sagittal view of
Figure 2B the irregularities of the postero-inferior wall of
the bladder are visualized. The presence of such irregularities
illustrate clearly the difficulties in applying a formula
for the estimation of volume. There is no appreciable
advantage in either plane in the ability to detect an echofree
space of the urinary bladder.
DISCUSSION
At the present time the detection of residual urine is done
by either catheterization after the patient voids or an intravenous
pyelogram with radiography of the bladder after
voiding. Particularly in the diabetic patient, both of the
above procedures have undesirable features. Catheterization
carries a small but significant risk of infection and,
especially in the male, may be an uncomfortable procedure.
Intravenous pyelography carries the risk of allergic
reactions ranging from urticaria to anaphylaxis. In addition it
is now recognized that only partly reversible renal insufficiency
may occur after intravenous pyelography in
diabetic patients. 8
Determination of the presence of a residual urine in the
diabetic patient is relevant to his treatment program in
many areas, such as, management of urinary tract infections
and reliability of the urinary glucose determination.
For these reasons it seemed desirable to establish whether
a noninvasive technique, such as ultrasonography, could be
used reliably to detect the presence or absence of a
residual urine in the bladder and, if so, at what resolution.
In the current study, the radiologists were asked to
interpret isolates as opposed to serial views of any
particular patient in the absence of clinical history. Of the
incorrect replies, in which an echo-free space was seen in
the empty bladder (group A-false positives), one was due to
a cystic-appearing prostate. Other false positives were
thought to represent incomplete bladder drainage due to
gravitational or mechanical factors.
In the other groups (B through D), incorrect replies
were false negatives, since fluid was known to be present
in the bladder. With larger volumes, the percentage of
false negatives decreased from 22 in group B to 0 in
group D. The false negatives were probably technical in
origin, such as might occur if the particular plane chosen
were to bypass the bladder. With residual urine volumes
of 100 cc, there is a 97% certainty of detection, with
virtual certainty at residual volumes of 150 cc and above.
These volumes are not large in the context of the diabetic
neurogenic bladder.
We feel that (1) ultrasonography affords an alternative,
safe method towards detection and diagnosis of postvoid
residual urine and (2) its application for this purpose
should be encouraged. Invasive methods should be reserved
for patients in whom the sonography results are
equivocal.
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