medical imaging: urinary and pelvic Flashcards
Label the image
- iliac crests
- ilium
- sacral foramina
- ileosacral joint
- anterior superior iliac spine
- anterior inferior iliac spine
- ischial spine
- superior pubic ramus
- obturator foramen
- ischial tuberosity
- inferior pubic ramus
- pubic symphysis
- coccyx
- diaphysis/ femoral shaft
- lesser trochanter
- reater trochanter
- neck of femur
- head of femur
- acetabulum
What are the areas highlighted on the pelvis and what muscles attach here?
- iliac crest –> abdominal muscles
- anterior superior iliac spine –> sartorius
- anterior inferior iliac spine –> rectus femoris
- greater trochanter –> gluteus medius and minimus
- lesser trochanter –> iliopsoas
- ischial tuberosity –> hamstrings
- symphysis –> adductors
How does the pelvis develop?
Each side of the pelvis forms as cartilage which ossify as three main bones which stay separate through childhood : ilium, ischium and pubis. At birth the acetabulum and top of the femur are still made of cartilage.
First elements to fuse are ischium and pubis which unite anteriorly to form ischiopubic rami at 4-8 yrs. Next ilium fuses to ischiopubic portion at the acetabulum between 11-15 in F and 14-17 in M to form the os coxa (pubic bone).
Seen on xray –> fibrocartilage between bones
How do you interpret a pelvic xray?
- Systematic review: Bones
- three rings –> main pelvic ring, two obturator foramina; if disrupted think fracture
- joint spaces –> sacroiliac joint symmetry and size 2-4 mm; symphysis pubis joint space less than 5mm; if joint space widened think main pelvic ring fracture
- Acetabulum -> trace ileopectineal line, ilioischial line, acetabular roof, anterior rim, posterior rim and teardrop (see picture).
- sacral foramina –> arcuate lines smooth and symmetrical
- Proximal femur –> cortex of femoral head, neck, greater and less trochanter should be smooth with normal trabecular pattern; trace shenton line; if disrupted think fractured proximal femur.
- Bowel gas
- radiopaque lesions
- soft tissue
What are the main rings to methodically look at in pelvic xray?
Pelvic brim and the two obturator foramen
Ensure the rings are intact
What are the lines to look over in pelvic xray?
Letournel lines: Iliopectineal line, ilioischial line, acetabular roof, anterior rim, posterior rim and teardrop
- posterior wall of acetabulum
- anterior wall of acetabulum
- roof of acetabulum
- acetabular teardrop
- ilioischial line (posterior column)
- iliopectineal line (anterior column)
- Ileopectineal line disruption suggests anterior column fracture (anterior column of acetabulum)
- ilioischial line disruption suggests posterior column fracture (posterior column of acetabulum)
- teardrop displacement suggests an occult acetabular fracture (occult = hidden and does not appear well on xray.)
What line is shown and what is this line important in identifying?
Shenton’s line important in identifying neck of femur fractures and very subtle impacted fractures.
Impacted fractures show as sclerotic high density lines, you will see a cortical step in shenton’s line.
What is shown and what should you make sure of on xray?
These are the sacral foramina, need to make sure all are aligned. Alignment will be slightly curvilinear.
after checking rings and lines what is checked next?
Joint spaces:
1) sacroiliac joints
2) pubic symphysis
Widening in both suggests large hip fracture
Narrowing suggests degenerative cartialginous disease
In ankylosing spondylolitis get narrowing as well as high density around sacroiliac joint
What checklist should you go through in pelvic xray
- iatrogenic lines –> central lines (femoral lines), urinary catheters etc
- bones:
- pelvic bones -> iliopectineal, ilioischial, shenton’s
- sacrum (foramina nad SIJ’s)
- lumbar spine (vertebra, pedicles, transverse/spinous process)
- Bowels (gas, faeces, dilation, thumb printing)
- radiopaque lesions (foreign body, calculi)
- soft tissue (oedema, emphysema)
- miscallaenous –> lytic lesions (think myeloma or underlying metastatic deposits), boney islands/ cysts (benign lesions, high density lesions) –> get senior involved.
What is the young and burgess classification?
- used prognostically and how to treat injuries
- lateral compression –> side on impact graded 1-3 with 3 being highest severity of injury
- AP compression with grades 1-3
- Vertical shear injuries are the worst type of injury; where patient has dropped from a great height and the force has been transmitted up lower limb to the hip bone
- When diagnosing a patient have in your mind the mechanism of injury; often history is highly important in making a diagnosis of type of injury
What are common fractures affecting the pelvis?
- most pelvic fractures result from trauma
- motor vehicle/ bike collision - 54%
- pedestrian vs motor vehicle - 30%
- fall from height -10%
- sports injury and low energy fall
- pelvic insufficiency (osteopenia) fractures are common in the elderly, only low impact required to disrupt bone
What are the imaging modalities available for the pelvis and what are their indications?
- xray –> quick and easy
- CT –> for trauma cases go straight to CT scan as anticipate multiple fractures, internal injuries. For more subtle acetabular/ ring fractures/ sacrum fractures, reconstruction planning purposes
- MRI –> not sensitive for fractures but useful for soft tissue structures e.g. ligamentous structures, and urinary/ gyne systems
What are potential complications for pelvic fractures?
- Pelvic bleeds:
- slow venous bleeds –> think psoad and retroperitoneal haematoma
- fast arterial bleed –> Think sheering force
- emboli may form due to interruption of normal blood flow
- Bladder or urethral rupture (vertical sheer) –> urogenital problems e.g. strictures and incontinence
- lower intestine/ rectum can also rupture
- damage to reproductive organs
- sciatic nerve injury
- persisten sacroiliac pain due to unstable pelvis
Treatment of pelvic fractures?
- Depends on the type of fracture; pelvic fractures often split and described as “stable” or “unstable.”
- Stable fracture –> often only one break in pelvic ring and no displacement of broken ends of bone. E.g. iliac wing fracture, sacrum fracture, superior/ inferior pubic ramus fracture.
- Unstable fracture –> usually two or more breaks in pelvic ring and ends of broken bone are displaced. More likely to occur due to high energy event. Examples are lateral compression fracture where pelvis pushed inward, AP compression fracture and vertical shear fracture where one half of pelvis shifts upward.
- Immobilisation for most –> minor fracture most common tx is bed rest, NSAIDS, physical therapy and crutches.
- Surgical –> external fixators –> metal pins/ screqs inserted into bones to stabilse pelvic area
- acetabular reconstruction (rarely)
What type of procedure produced this image?
Label the image
Intravenous urogram = procedure used to visualise abnormalities of urinary system.
- right pelvis
- right ureter
- right uretovesical junction
- bladder
- liver
- major calyx left kidney
What structures are shown on this MRI?
- Anteriorly see the abdominal muscles coming down to attach at the pubic symphysis
- posterior to that the bladder
- posteriorly to that a retroverted uterus and vagina
- even more posterior see the sigmoid colon, rectum and anal canal
- most posterior sacrum and lumbar vertebrae
What is a micturiting urethrocystogram?
Contrast given via urinary catheter; image established through fluoroscopy using Xray.
Can look for strictures, especially important post TURP (transurethral resection of the prostate) to ensure there is no urethral leak into the pelvis.
What imaging modalities are available for the urinary system?
- xray/ urethrocystograms –> look for radioopaque stones, strictures, post- op leaks
- CT –> nephritis/ pyelonephritis; hydroureter/ nephrosis/ calculi
- MRI –> good for soft tissue definition, if suspect urology or gyne cancer, lymph nodes
40 yr old male R loin - groin pain for past 3 days now worsening in intensity in Right iliac fossa
Differentials?
- ureteric colic
- testicular torsion
- pyelonephritis
- appendicitis
What imaging would you use if suspected urolithiasis?
- urolithiasis –> stones in bladder/ urinary tract
-
First line –> ultrasound: (to minimise risk of radiation)
- hyperechoic focus (sound waves echo, sound waves come back stronger due to high density stone).
- posterior acoustic shadowing (due to high density stone, some sound waves do not get through, posterior shadowing occurs).
- less sensitive than CT for smaller stones
- Second line –> CT KUB (kidney, ureter, bladder); 99% sensitive for renal tract stones
- x-rays rarely done for suspected urolithiasis
What types of renal stones are there?
What types are radiopaque and will be picked up on xray?
what stones will NOT be picked up on xray?
-
Urolithiasis:
- calcium oxalate +/- calcium phosphate = 75%
- struvite stones (triple phosphate) = 15%
- pure calcium phosphate = 5-7%
- uric acid 5-8%
- cystine 1%
- any stone that contains calcium or phosphate will be radiopaque
- uric acid and cystine stones are radiolucent and will not be picked up on an xray
What can be detected on these US scans?
- stone wedged within the ureter –> hyperechoic region and posterior shadow
- any blockage in any tube –> distal to the blockage there will be collapse and proximal to the blockage there will be dilatation
- proximally hydroureter and distally collapse
- Picture on the right; urolithiasis near the vesico-ureteric junction
What is shown on this CT scan?
Right sided ureter dilatation –> proximal hydroureter
What is shown on this CT scan?
R sided urolithiasis within the right ureter
What are the risk factors for urolithiasis?
- dehydration
- urinary tract malformations –> horseshoe kidney or duplex kidney
- urinary tract infections
- homocytsinuria (disorder of methionine metabolism, leading to an abnormal accumulation of homocysteine and its metabolites (homocystine, homocysteine-cysteine complex, and others) in blood and urine)
- hypercalciuria –> primary hyperPTH and vitamin D intoxication
- high uric acid levels –> gout/ dietary/ familial
Differentials for :
32 Female with Right iliac fossa pain, fever and vomiting
- Appendicitis
- Ureteric colic
- Ectopic pregnancy
How would you investigate for :
32 Female with Right iliac fossa pain, fever and vomiting
- First line –> ultrasound –> THINK! Radiation exposure for a reproductively active female
- second line –> CT abdomen and pelvis
Differential diagnosis for:
75 male with known colorectal cancer presents with AKI and confusion
- Differentials:
- dehydration
- iatrogenic (diuretics)
- metastatic disease
How would you investigate for previous patient?
- As you already suspect metastases first line is CT KUB
Case 4: 20 female with vague abdo- levic pains, recurrent UTI in the past
What are you differentials?
How would you investigate?
- Pelvic inflammatory disease (systemically unwell)
- pregancy (normal/ ectopic)
- ovarian torsion (pain + + +, sympathetic response, Hypertensive, tachycardic, sweating)
- First line investigation –> ultrasound
Why must someone fill their bladder before an USS pelvic scan?
- In any fluid filled space with ultrasound the echoes travel and cast an enhancement –> posterior acoustic enhancement of the bladder
- The structure shown behind the bladder is the uterus
Why is ultrasound used in pelvic imaging?
Ultrasound useful for localised pathology and useful to prevent radiation exposure to children and women of childbearing age
Why is CT used in pelvic imaging?
CT useful for looking for systemic pathology/ unclear source of symptoms
What is the abnormality shown?
Right iliac crest there is a fracture line
Note it is just a bowel line crossing the pubic symphysis
What is the abnormality shown on this left sided USS scan?
Hydropnephrosis –> dilated left pelvis and major and minor calyces
What is the abnormality shown?
Diastasis of the pelvis plus left sided disruption of the sacroiliac joint
what is the abnormality?
right sided pubic ramus fracture plus left sided hip replacement
