Ch 32 Diaphragm Flashcards
Emrbyologically, the diaphragm is formed by
- Septum transversum (ventrally)
- foregut mesentery and 2 pleuroperitoneal folds (dorsally)
Movement of the diaphragm provides approximately ___ % of the change in intrathoracic volume during quiet respiration, and the ____ provide the rest.
- 75
- intercostal muscles
Lymph flow is unidirectional/bidirectional. What is the final destination of lymph?
unidirectional
thoracic trunks
Parts of the diaphragm
Tendinous centre
3 thin peripheral muscles:
- pars lumbalis (R and L crura)
- pars costalis
- pars sternalis
Where do the crura of pars lumbalis attach?
L3 body / L4 cranioventral border
Which part of the diaphragm attaches to L3/L4?
Pars lumbalis crura
Where does pars costalis of the diaphragm attach?
8-13th rib
Where does pars sternalis of the diaphragm attach?
xiphoid process cartilage
From dorsal to ventral, what are the openings in the diaphragm?
aortic hiatus
esophageal hiatus
caudal vena cava foramen
what passes through the aortic hiatus?
aorta
azygos
hemiazygos veins
lumbar cistern of thoracic duct
what passes through the esophageal hiatus?
esophagus
vagus nerve trunks
what passes through the vena cava foramen?
caudal vena cava
Where is the caudal vena cava foramen located?
at the junction of the muscular and tendinous portion of the diaphragm
Which 2 recesses does the diaphragm form?
phrenicocostalis
phrenicolumbalis
DV or VD?
VD
DV or VD ?
DV
LL or RL?
LL
LL or RL?
RL
What / where is the intercrural cleft?
- a shorter convex, opaque line caudal and ventral to the crura
In which recumbency are the crura parallel?
RL
In which recumbency are the crura crossed?
LL
What do the crura do in RL and LL?
RL: parallel
LL: crossed (sometimes)
What can be a cause of the appearance of the crura to be extensively separated (by up to 2.5 vertebral lengths)?
- rotation of the patient
- XR beam centre over cranial or mid thorax
What can be used to distinguish RL from LL?
confluence of the CVC with the right crus of the diaphragm
- in RL this will be the cranial crus
When is a single domed diaphragm seen on a VD?
when XR beam is centred over mid-abdo
When is a single domed diaphragm seen on a DV?
when XR beam is centred over mid-thorax
When is a 3-domed diaphragm seen on a VD?
when XR beam is centred over mid-thorax
When is a 3-domed diaphragm seen on a DV?
when XR beam is centred over mid-abdo
What is the normal intersection point of the diaphragm and the spine, and what is the normal variation?
(T9-)T11 - T13 (-L1)
How many vertebral lengths does normal respiration affect the diaphragm position?
1/2 - 2
In cats, the diaphragmatic crura change position equally on different projection, as with dogs. True or False?
False; variation is much smaller and distinction of diaphragmatic anatomy is more challenging (probably too small?).
RL or LL (cat)?
LL
RL or LL (cat)?
RL
2 causes of a more convex and cranially extending diaphragm?
2 causes of an asymmetric diaphragmatic shape
- unilateral tension pneumothorax
- hemiparalysis
Which way (cranial / caudal) will the diaphragm shift with a generalised paralysis?
Cranial
2 causes of bilateral caudal displacement of the diaphragm
- Severe respiratory disease
- Bilateral tension pneumothorax
What is the most common cause of diaphragmatic hernia?
Abdominal trauma; high momentary increase in abdominal pressure when the glottis is open > high pleuro-peritoneal pressure gradient
To ascertain the position of the stomach and proximal small bowel, a small amount (______ ml/kg) of ______ (___% w/v) can be given orally and radiographs obtained after _______minutes.
0.5 ml/kg of barium sulfate 30% w/v
15-20 minutes
Positive-contrast peritoneography can be performed by injecting _____ mL/kg body weight of ___________ contrast medium into the peritoneal cavity.
2
an iodinated, preferably nonionic,
which side of the diaphragm herniates more frequently in dogs?
right
The (5) organs that most frequently acuteky herniate are, in order of prevalence, the:
liver, small bowel, stomach, spleen, and omentum
Which organs are reported in chronic herniations (not acute)?
colon and pancreas
Why is gastrothorax a potentially life-threatening state?
cardiac tamponade
Presence of pleural fluid can distinguish the diaphragmatic hernia from thoracic pathology - T or F?
False; Pleural fluid is present consistently with chronic diaphragmatic hernias, or if a herniated abdominal organ, most usually the liver, is strangulated through a small diaphragmatic opening.
which ‘sign’/ structure is specific to cats with PPDH?
dorsal peritoneopericardial mesothelial remnant
Approximately ___% of all diaphragmatic hernias are congenitally predisposed.
15
A peritoneopericardial diaphragmatic hernia occurs when abdominal viscera herniates into the pericardial sac through a _________ formed between the _________ and the ________.
- congenital hiatus
- tendinous portion of - - the diaphragm
pericardial sac
PPDH may have what genetic pattern in cats?
Overrepresented breed(s)?
Rate of incidence?
autosomal recessive
DLH, Himalayans
1:500 - 1:1500
PPDH is always clinical - T or F?
Peritoneopericardial hernias may produce clinical signs, but are often an incidental radiographic finding.
Most common PPDH herniating organ?
liver
Which hepatic condition is associated with PPDH herniation?
hepatic cysts
other differentials for large rounded cardiac silhouette (other than PPDH)?
pericardial effusion, generalized heart enlargement, or both
Hiatal hernias occur when ______ enters the thorax through the ________.
a portion of stomach
esophageal hiatus
3 causes of hiatal hernias
- enlarged esophageal hiatus: congenital (1), trauma (2)
- contraction of the longitudinal esophageal muscle (3)
2 types of hiatal hernias
sliding and paraesophageal
Which type of hiatal hernia is usually congenital and found in younger animals?
sliding
With which condition is sliding hiatal hernia associated?
esophagitis from gastroesophageal reflux
which anatomical structures move with a sliding hiatal hernia?
The gastroesophageal sphincter and a portion of stomach (usually cardia) are herniated into the thorax.
The caudal esophagus and the cardia slide intermittently from the abdomen into the thorax, causing temporary cranial displacement of the thoracic esophagus.
what is a non-sliding hiatal hernia?
the gastroesophageal sphincter and the gastric cardia displaced through the esophageal hiatus and fixed within the thorax
what is a paraesophageal hiatal hernia?
- the cardia or cardia and fundus, or other soft tissue structures herniate through or alongside the esophageal hiatus and become positioned adjacent to the esophagus
- usually static and do not slide between the thorax and abdomen, and the gastroesophageal sphincter is in a normal position.
which breed has hiatal hernias in association with other esophageal issues (dysmotility and redundancy)?
shar-pei
What findings to expect with esophagram of hiatal hernia?
Which type of tumor has been reported to originate from the diaphragm?
peripheral nerve sheath tumor
(1y FN GSD - 1999, 11Y MN Greyhound - 2008)
Etiology of peritoneopleural hernias
Congenital; The defects are created when the septum transversum or the pleural peritoneal folds do not develop and fuse to form a complete diaphragm.
Pleuroperitoneal hernias occurring in the muscular location are reported in which location?
Dorsolateral
Pleuroperitoneal hernias occurring in the membranous portion are associated with which other condition?
Umbilical hernias
What is the most consistent sign of a sliding hiatal hernia?
displaced stomach
The cardia appears to be stretched toward the diaphragm or may extend into the thorax. This displacement produces an abnormal shape to the cardia and fundus remaining in the abdomen. The caudal esophagus may or may not be distended, and a soft tissue mass may be seen adjacent to the left diaphragmatic crus
How long is the caudal esophageal sphincter?
1-2cm
“The caudal esophageal sphincter can be identified as a concentric, smooth, 1- to 2-cm narrowing in the caudal esophagus “
Signalment for gastroesophageal intussusception
young, male GSD
also animals with pre-existing dilated esophagus
Does barium enter the stomach with an esophagram of a gastroesophageal intussusception?
No, but rugal folds may be outline.
Is gastroesophageal intussusception incidental or clinical?
Gastroesophageal intussusception usually produces an esophageal obstruction, which results in rapid deterioration of the animal’s condition with a high mortality rate; a timely diagnosis is therefore essential.
Besides the stomach, what else can herniate in a gastroesophageal intussusception?
spleen, duodenum, pancreas, omentum
With membranous defects of the diaphragm, what structure is displaced in dogs?
Liver
With membranous defects of the diaphragm, what structure is displaced in cats?
Falciform fat
Why do displaced structures (in membranous defects) remain in the ventral thorax and are confined to the mediastinum?
because the peritoneum and pleura are still intact
innervation of the diaphragm
phrenic nerve
types of motor dysfunction of the diaphragm
paralysis (unilateral or bilateral)
flutter
causes of diaphragmatic paralysis
- pneumonia, trauma, myopathies, and neuropathies, or the cause may be unidentified
Transient diaphragmatic paralysis has been reported as a consequence of what, in which species?
post-traumatic
2 cats
unilateral paralysis
What kind of movement occurs with bilateral diaphragmatic paralysis?
no movement, minimal or paradoxical (cranial during inspiration)
Why can bilateral diaphragmatic paralysis be difficult to diagnose even on fluoro?
diaphragmatic movement is sometimes produced by compensatory abdominal muscle contraction during respiration
What is diaphragmatic flutter and how is it diagnosed??
contractions of the diaphragm synchronous with the heartbeat
- usually transient, Dg on fluoro
Muscular dystrophy in cats has which imaging features of the diaphragm?
Muscular hypertrophy occurs, and affects the diaphragm (giving it a scalloped appearance at the ventral margin) and the esophagus (causing extrahiatal obstruction > megaesophagus). This is seen after 7 mo of age.
Muscular dystrophy in dogs has which imaging features?
In dogs with muscular dystrophy, radiographic abnormalities include:
- diaphragmatic asymmetry
- diaphragmatic undulation
- gastroesophageal hiatal hernia
