bladder anatomy uchendu
TRANSCRIPT
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Question:
Describe the radiological anatomy of the male urinary
bladder. Describe in detail the techniques fordemonstrating the organ.
Answer
- Introduction/Gross- Imaging Modalities:
* Cystogram* Pelvic scan
* CT scan* MRI* Plain radiography* Angiography
* RNI
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- Introduction/Gross
The urinary bladder is situated within the
pelvis. It is an extraperitoneal pyramidalmuscular organ when empty but as it fills,
it becomes ovoid and rises into the
abdomen stripping the loose peritoneumoff the anterior abdominal wall.
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It has a base/posterior surface, an apex, asuperior and two inferiolateral surfaces. The
ureters enter the posterolateral angles and theurethra leaves inferiorly at the narrow neckwhich is surrounded by the involuntary internal
urethral sphincter. The trigone is the triangularinner wall of the bladder between the uretericand the urethral orifices, this part of the wall is
smooth while the remainder of the bladder wallis coarsely trabeculated by crisis- cross musclefibres.
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The perivesical fat surrounds the bladder.
The bladder is relatively fixed inferiorly viacondensations of pelvic fascia, which attach it to
the back of the pubis, the lateral walls of the
pelvis and the rectum. The obturator internus
muscle is anterolateral and the levator ani
muscle is inferolateral to this.
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The vasa deferentia and seminal vesicle
are posterior to the bladder so also is
the cul-de-sac and rectum. Thebladder neck is fused with the prostate.
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Imaging Modalities
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CystogramIt localises the bladder within the pelvis
cystogram is used to assess the integrity ofbladder following trauma or surgery or toinvestigate fistulas involving the bladder. Thebladder is filled with contrast which appear asrounded radio-opacity and demonstrates the
corrugation of the bladder wall especially whennot well distended.
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The bladder wall is seen as the soft tissue
density structure separating the perivesicalfat and the intravesical contrast
Irregular collection of contrast may be
trapped between muscles fibres aftermicturition the prostate may protrude up
into the bladder base to produce a prostatic
impression the full bladder outline shouldbe smooth and regular
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Pelvic US
Us is best for demonstrating the internal
anatomy. Routine examination of the bladderrequires it to be moderately full. The normalbladder has a triangle shape in the sagittal plane
and that of a square with the corners roundedoff in the transverse plane. The normal wallthickness is 2-3mm when the bladder ismoderately full. The bladder wall is slightly
echogenic which contrasts against the anechoicurine within it this beautifully demonstrating theinternal anatomy.
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It is also possible to visualize the lower ureter inyoung children and the use of colour Doppler
allows identification of ureteric jet
Relations, Anterior, Anterior abdominal wall(medium level echo), Pubic bone (posterior
acoustic shadow) Posterior: Rectum (poorly demonstrated)
Lateral: Obturator internus muscle (medium
level echo), levator on muscle (medium levelecho)
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Superior: Loops of bowel (not properly
demonstrated because of bowel gas;
evidence of peristalsis)
Inferior: Prostate (lobuted out line,
homogenous medium level echo)
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CTThe bladder is best appreciated when filled withurine or contrast and it is seen as a thin walledstructure between the urine and the periversicalfat the wall should not exceed 4-5mm fat. Theappearance of the urine depends on thepresence or absence of contrast, when present it
hyperdense but when absent it is hypodense
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The seminar vesicles which lie on the posteriorwall of the bladder appear as tubular structurerelated to the superior aspect of the prostateand posterior to the lower bladder but anteriorto the rectum. There is a fat plane between the
seminal vesicles and the bladder. In asuprapubic axial slice, the various structuresfrom anterior to posterior are
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i Anterior abdominal wall [(subcut. fat (hypodence);rectus abdominic (isodense)]
ii Urinary Bladderiii Seminal vesicle (isodense)
iv Rectum (gas + faeces + contrast => mixed density)
v Sacrum (hyperdense)vi Gluteus maximus (isodense)
vii Subcuit fat (hypodense)
Psoas muscles are demonstrated laterally at higher levelbut obturator internus muscle at lower levels
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MRI
MR is ideal to demonstrate the relationshipof the bladder in the coronal and sagittal plane.It is seen as a low/ intermediate signal line on t1W images, similar to urine hence poor contrast
between them but on T2 W1 the bladder wall isseen as a thin low signal intensity line adjacent tothe high signal of fat outside and urine inside the
bladder
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The bladder wall enhances intensity with IV
gadolinium.
On T2 W1 the seminal vesicle is hyperintense but
it has intermediate intensity on T1 W1.
NB- They low intensity bladder wall may beobscured by the chemical shift artifact that result
from the difference in resonance frequency
between fat and water proton
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Plain Radiograph.
The bladder may be identified on plain filmespecially when full. It is seen as a round softtissue density surrounded by lucent line ofperivesical fat. It should be smooth and
symmetrical.
Angiography
This demonstrates the superior and interiorvesical artery originating from the internal iliacartery as radio opaque lines
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RNI (Radionuclide Cystography)
AgentNon absorbable radiotracer e.g. 99M TC-MAG3 (Mercaptoacetylglycine)
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B. Describe in detail the technique fordemonstrating the urinary bladder.
- Outline
Indications
C.I
Patient preparation
Equipment/materials
Techniques proper description
After care
Complication
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(1) Cystogram
Indications(i) Abnormalities of the bladder e.g. fistula
mass
(ii) After bladder trauma(iii) After bladder surgery
(iv) Haematuria
(v) Difficulty in micturition
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C.I
Acute urinary tract infection Patient preparation
(a) The patient micturates prior to the exam
(b) Patient is fasted for about 6hrs prior toexam
Contrast medium
HOCM or LOCM
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Equipment/Materials
(1) Fluoroscopy unit with spot film device(2) Jaques or foley catheter. In small infants a fine
(5-7F) feeding tube.
(3)
Casettee and film(4) Emergency tray
(5) Sunctioning machine
Preliminary filmConed view of the bladder
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Technique
(a) The patient lies supine on the x-ray table.
Using aseptic technique a catheter, lubricatedwith Hibitane 0.05% in glycerine, is introducedinto the bladder. Residual urine is drained.Contrast medium is slowly dripped in a bladderfilling is observed by intermittent fluoroscopy.It is important that initial filling is monitoredby fluoroscopy in case the catheter is in the
distal ureter (Therapy mimicking vesicouretericreflux) or vagina.
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(b) Any reflux is recorded on spot films
(c) The catheter should not be removed untilthe radiologist is convinced that no more
contrast medium will drip into the
bladder.(d) Film are taken in AP, lateral and oblique.
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Aftercare
(A) No special aftercare is necessary, but patientsand parents of children should be warned thatdysuria, possibly leads to retention of urine,
may rarely be experienced. In such cases asimple analgesic is helpful and children may behelped by allowing to micturate in a warmboth.
(B) Antibiotics should be prescribed if reflux isdemonstrated.
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CX
(A) Due to the contrast medium Adverse rxn may result from absoprtion of
contrast medium by the bladder mucosa Contrast medium-induced cystitis
(B) Due to the technique
(a) Acute U.T.I
(b) Catheter trauma-may producedysuria, frequency, haematuria andurinary retention.
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(c) Complications of bladder filling e.g.perforation from overdistentionprevented
by using a non-retaining catheter e.g. Jaques.(d) Retention of a foley catheter
(2)
U/S* Indications(i) Haematuria(ii) Bladder outlet obstruction(iii) Bladder tumour and other pelvic masses(iv) Post trauma
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C.I
None Patient preparation
Full bladder
Equipment/material(a) 3.5SMHz transducer
(b) U/S machine
(c) Electrolyte/Ultrasound gel
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Technique
The patient lies supine and the bladder isscanned suprapublically in transverse and
longitudinal planes. Measurement taken of
three diameters before and aftermicturition enable an approx. volume to be
calculated.
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After Care
None Cx
None
3)Pelvic CT Indications
as already stated C.I
(i) rxn to contrast medium(ii) Pregnancy
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Patient preparation
- Bowel preparation
- Fast in the day of exam
- Give 500ml dilute contrast agent orally the eveningpreceding exam
Equipment/Materials
(a) CT Machine
(b) CT Printer
(c) Contrast agents(d) Mechanical injector
(e) Emergency tray
(f) Suctioning machine
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Technique
We give 500ml dilute contrast agent orallythe evening preceding the exam and repeat thedose 45 to 60min before the exam. The colonand the rectum can be distended by placing atube in the rectum and insufflating with 20 puffsof air, or the limit of patient comfort. Allpatients are asked to avoid micturition for 30 to
40min before the exam to allow bladder filling.IV
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contrast medium is routinely given bymechanical inject or at 2 to 3ml/sec for a total
dose of 150ml of 60% contrast agent. Lie patientsupine angulate your gantry. Scanning throughthe pelvis is performed with contiguous 2-5mm
thick slices. We routinely scan the abdomen aswell in patients with known or suspected pelvicmalign.
N.B: A contrast material enema (200ml)occasionally may be necessary to expediteopacification of Rectosigmoid
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After Care
None Cx
Rxn to contrast
4)MRI Indication
As previously stated
C.IMetallic prosthesis or metals in the bodye.g. bullet.
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Patient preparation
No special preparation
Equipment/Materials
(i) M.R. machine
(ii) Gadolinium
(iii) M.R. printer
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Technique
Patient are usually examined supine duringshallow respiration, with the urinary bladder atleast half full before the study is begun.
Both T1-W (TR=300-500msec, TE=15
35msec) and T2W (TR = 1,500
2,100 msec,TE = 90-120 msec) spin echo sequences arenecessary for complete examination of thepelvis. T2W1 provide clear delineation of thebladder wall, as well as internal morphology ofthe prostate gland and the uterus.
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Transaxial images are obtained in every case;
additional views are performed in either thecoronal or sagittal plane. Coronal images areuseful for evaluating the seminal vesicle andbladder neoplasms that involve the lateral wallwhile sagittal images are necessary is cases inwhich a bladder neoplasm is located along theanterior or posterior wall.
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After Care
None
Cx
None