Ch 85 Diaphragmatic hernia Flashcards
anatomy
- musculotendinous partition, assists in ventilation, and movement of lymphatic fluid
- central tendinous section attach at 13th rib
- each crus (lumbar muscles) has tendon arising from 3rd and 4th lumbar vertebra
- costal muscles: arising from proximal 13th rib, distal 12th rib, costochondral 11th rib, all 10th and 9th ribs
- sternal muscle originates on the base of the xiphoid cartilage
- convex thoracic surface covered by endothelial fascia and pleura (continuous with mediastinum)
- dorsal to oesophagus pleura attaches to midline diaphragm
- pleural reflection (plica venae cavae), caudal to heart around vena cava, attaches to diaphragm
What are the three muscular components of the diaphragm?
How much of the diaphragm is composed of the central tendinous portion?
Pars lumbaris (right and left crus)
Pars costalis
Pars sternalis
Central tendinous portion approx 21% of surface area
Where do the splanchnic nerves and sympathetic trunk pass through the diaphragm?
Between the lateral portion of the crus and the 13th rib on each side
What are the three major openings of the diaphragm and what passes through each?
Caval foramen
- Caudal vena cava (adventitia fuses with central tendon with no extra space around cave)
- lies to the RIGHT
Oesophageal hiatus
- Oesophagus and its blood supply
- Dorsal and ventral vagal trunks
Aortic hiatus
- Aorta
- Azygous and hemiazygous veins
- Lumbar cistern of thoracic duct
What are the foramina of Morgagni?
Minor opening between the costal and sternal attachments of the diaphragm which allow the egress of the cranial epigastric arteries (termination of internal thoracic arteries)
Herniation through these openings is known as a retrosternal or Morgagni hernia
What is the major source of lymphatic drainage from the peritoneal cavity?
stomata within the diaphragmatic peritoneum
Drains to sternal LNs
blood supply to the diaphragm
principally from the main phrenic arteries (from phrenicoabdominal)
drained by a cranial phrenic vein > phrenicoabdominal
Where do the phrenic nerves arise?
sole motor innervation
Dogs: C5, C6, C7
Cats: C4, C5, C6
embryology
diaphragm forms from:
- septum transversum (initially incomplete between pericardium and peritoneum) > originates cervical vertebrae and migrates caudally turns into central tendon
- mesoesophagus (caudal mediastinum),
- pleuroperitoneal folds (close the pleuroperitoneal canals by fusion with the esophageal mesentery )
- body wall mesenchyme > create costal muscles
physiology
- Contraction of the diaphragm during inspiration pushes caudally on the viscera
- contraction of the diaphragmatic costal muscles produces expansion of the caudal rib cage
- chest wall expansion is produced by contraction of inspiratory intercostal muscles on the lateral walls
- diaphragmatic paralysis (bilateral phrenic n. cut) likely results in respiratory insufficiency
List the surgical approached for D-hernia repair
- Midling coeliotomy
- Caudal median sternotomy (extended ceoliotomy for irreducible hernia caused by thoracic adhesions.)
- Minimally invasive via resection of the xyphoid
- 9th intercostal thoracotomy
- Laparoscopic or thoracoscopic
Traumatic Diaphragmatic Hernia
Etiology, epidemiology
- Mechanism for indirect injury to the diaphragm = sudden increase in intraabdominal pressure (IAP) with the glottis open
- Application of force to the abdominal cavity with the glottis open increases the peritoneal-to-pleural gradient, and herniation of viscera is usually immediate after the diaphragm ruptures
- multisystem injury and shock
- Pulmonary contusion, pleural effusion, hemothorax, pneumothorax, and rib fractures
- 2% of dogs with fractures have a diaphragmatic hernia
- costal muscles are more often ruptured than the central tendon
- L=R, 15% being bilateral or multiple
- herniated: liver #1 >intestine > stomach, spleen, omentum, pancreas, colon, cecum, and uteru
difference in contents based on side of hernia:
right-sided
- the liver
- small intestine
- pancreas
left
- stomach,
- spleen,
- small intestine
What percentage of D-hernias are traumatic?
85%
What is the normal pleuro-peritoneal pressure gradient during relaxed inspiration?
What does this increase to during maximal inspiration?
Normal 7-20cm H2O
Maximal inspiration 100mm H2O
What are the most common forms of diaphragmatic tears in dogs and cats?
Dogs:
- 40% circumferential
- 40% radial
- 20% combination
Cats:
- 59% circumferential
- 18% radial
pathophysiology
GIT, Thorax, Liver, shock
- Pathologic effects result from effects on cardiorespiratory dynamics or on the herniated organs themselves.
GIT
- viscera can become inflamed, incarcerated, obstructed, or strangulated
- Incarceration of the stomach and intestine > partial or complete obstruction + compression of caudal vena cava and lungs
- compromised blood supply can also induce ischemic necrosis, intestinal perforation
LIVER
- Major effects of liver herniation: hepatic venous stasis, necrosis, biliary tract obstruction, and jaundice.
- Pleural effusion may develop with herniation of the liver into the pleural cavity
- Hydrothorax and ascites develop in approximately 30% of animals with liver herniation
THORAX
- Hemothorax, urothorax, chylothorax, bile pleuritis, and pneumothorax also possible
- lack of a functioning diaphragm, lung compression, and shock, respiratory insufficiency may result from hernia
- Parietal pleural contact with the lungs maintained by negative intrapleural pressure of 0.5 to 1.0 mm Hg > diaphragm rupture > parietal pleural contact with the lungs is lost
- abdominal and thoracic wall muscles take over the function of the diaphragm > fatigue
- hypoventilation, ventilation-perfusion mismatch, and hypoxia.
SHOCK
- reduction in effective perfusion, tissue hypoxia, and multiorgan failure
- Cardiac dysrhythmias
- al lead to fatal cardiopulmonary decompensation
What is said to be normally resident in healthy liver which can proliferate when hepatic blood supply is curtailed?
Clostridia-like anaerobic bacteria
What are normal pressures within the hepatic venous system?
What pressure is required for hepatic venous congenstion?
- Portain vein 8-12 mmHg
- Intrahepatic sinuses 3-4 mmHg
- Hepatic veins and Caudal vena cava 0.5-1 mmHg
If hepatic venous or caudal vena cava pressure increases to 0.85 mmHg beyond intrahepatic sinusoidal pressure, involved liver lobes become congested
Parietal pleural contact with the lungs maintained by negative intrapleural pressure of:
0.5-1 mmHg
diagnosis
- interval between trauma and diagnosis ranged from hours to 6 years, with a mean of several weeks
- heart sounds are muffled,
- location of cardiac apex beat is 80% accurate in determining the side of the hernia
RADs
- most useful view > lateral
- Partial loss of the normal line of the diaphragm in 66% to 97%
- viscera in the thorax
- obscure cardiac shape
- Lung lobe collapse and pleural fluid
- erect VD view horizontal beam (visceral shifting)
- contrast studies: may help (barium, positive-contrast peritoneography) but false-negative result occur
ultrasound
- accuracy of 93% for the diagnosis of diaphragmatic hernia
- useful when pleural fluid present
How do the crura appear in each lateral radiograph?
Parallel in right lateral
Cross over/Y shaped in left lateral
What contrast studies have been reported for D-hernia diagnosis?
- Barium swallow study
- Pneumoperitoneography
- Postivie-contrast pleurography
- Portography
- Cholecystography
- Angiography
If the hernia is plugged by viscers, false-negative can result
Timing of Surgery
- earliest opportunity in a stable patient, taking into account other injuries
- timing of surgery affected survival rates: death in the early group was entirely a result of shock and trauma (win 24hr)
- case series: 63 patients that underwent surgery within 24 hours of admission to hospital 93.7% survival
- Delays in surgery place the patient at risk for life-threatening hypoventilation from compression of the lungs by the abdominal viscera
- Acute gastric gaseous distention effectively produces a tension pneumothorax > emergency decompression required
- wait 3 to 7 days after herniorrhaphy before reanesthetizing the animal for fracture repair
peri-op care
- stabilisation
- O2 flow
- rapid induction to have control of airway
- may be necessary to tilt the table to elevate the patient’s head and thorax and relieve pressure on the lungs.
- ab’s if liver herniation
What inspiratory pressure should be avoided during ventilation for a D-hernia?
Avoid ventilation pressures over 20 cm H2O
hernia reduction
- Traumatic hernias may have multiple rents
- reduced by gentle traction
- swollen or adherent > rent in the diaphragm is enlarged (avoid phrenic vessels and nerves, caudal vena cava)
- Intrathoracic adhesions divided under direct observation (may require caudal median sternotomy)
- adhesions <7 to 14 days = fibrin and little organized fibrovascular tissue, digital manipulation.
- Mature organized adhesions are divided by precise sharp separation, electrocautery
Hernia Closure
- horacic cavity can be lavaged with warm saline.
- organs are carefully inspected for viability
- thoracostomy tube or tube can be exited through the diaphragmatic closure and out the abdomen
- Reestablishment of negative pressure is not necessary after hernia repair and may be detrimental
- debridement of the edges of chronic hernias to stimulate healing is controversial
- Suture closure dorsal to ventral
- polydioxanone or polyglyconate) in (3-0 to 0 USP)
- continuous patterns are preferred over an interrupted suture pattern
- near the caudal vena cava > avoid obstructing venous return
- circumcostal > sutures can be anchored around the costal arch
- rostral advancement of the diaphragm produces satisfactory clinical results
How does laparoscopic stapling of the diaphragm compare to open suturing?
Laparoscopic stapling is inferior
List some alternative methods of closure of a D-hernia (7)
Atrophy and fibrotic contraction of the chronically torn diaphragm
- Omentum - too weak to provide adequate support alone (double layer of omentum, stimulates angiogenesis and promotes wound healing)
- Muscle - 10% larger than the defect when developed (transverse abdominis 13th rib as base, rectus abdominis, latissimus dorsi)
- Liver
- Fascia
- Collagenous xenographs
- Polypylene mesh
- Silicon rubber sheeting
pulmonary reinflation
- Some clinicians leave residual air within the thoracic cavity, removing it only if respiration is compromised
- reestablish negative intrathoracic pressure is potentially dangerous
- Airway pressures should not exceed 20 cm H2O pressure
- Chronically atelectatic lungs should be reinflated by gradual reexpansion (rupture, reperfusion injry)
- continuous maintenance of 10 cm H2O negative intrapleural pressure, these lung lobes reexpand gradually over several hours
What is the Valsalva effect?
A dangerous reduction in venous return due to unduly prolonged expansion of the lungs while suturing
What are potential effects of overinflation of traumatised lungs?
Rupture of pulmonary parenchyma:
- Intrapulmonary haemorrhage
- Pulmonary oedema
- Pneumothorax
post-op considerations
- Therapeutic antibiotics are unnecessary unless the liver herniated or injured or GIT perforated.
- cardiovascular and respiratory status is monitored
- may develop hypoventilation, hypoxia, and respiratory acidosis from inadequate thoracic expansion
- thoracostomy tube allows early detection and correction of respiratory compromise > 2-3 mL/kg/d of fluid tube pulled
- Reexpansion Pulmonary Edema
- Pneumothorax
- Abdominal compartment syndrome
What is reexpansion pulmonary oedema?
tx?
An inflammatroy response to lung expansion that causes increased capillary permeability
Presumable due to expansion-related mechanical injury to alveolar capillary membrane and reperfusion injury
- Treatment: hemodynamic support, oxygen, diuretics, bronchodilators.
- patients may require ventilation and positive end-expiratory pressure
- guarded prognosis
List potential causes of post-op pneumothorax
- Handling suring surgery
- Damage during break down of adhesions
- Reinflation injury
Intraperitoneal Pressures
abdominal compartment syndrome
- chronic hernias may experience a loss of abdominal domain as a result of abdominal wall contraction or underdevelopment
- replacement of abdominal viscera, closure may result in significant increase in intraabdominal pressure (IAP).
- Aggressive pain control has made a significant difference in many patients
List potential effects of abdominal compartment syndrome (6)
- Decreased renal function
- Hypotension (decreased CO)
- Hypoxia (reduced ventilation and lung compliance)
- Visceral hypoperfusion
- Acidosis
- Increased ICP
How can intra-abdominal pressure be measured?
What is considered normal?
Can be measures with an indwelling urinary catheter
- IAP 5-10 mmHg - monitored and adequately hydrated
- 11-20 mmHg - Medical treatments instituted
- Over 20 - Surgical decompression
What are the medical(3) and surgical(5) options for abdominal compartment syndrome?
Medical
- Analgesics (Epidural catheters, wound “soaker” catheters, CRIs, opioid)
- Evacuation of intraperitoneal contents (fluid/air)
- Evaculation of intraluminal contents (urine, gastric air)
Surgical
- Surgical mesh
- Removal of spleen
- Advancement of diaphragm
- Relaxing incisions in external rectus sheath
- Leave linea unapposed
What is the prognosis for traumatic D-hernias?
Approx 15% die before arriving to hospital
Survival to discharge 82-89%
prognosis
- Poor anesthetic management and inadequate ventilation have been blamed for intraoperative deaths
- Complications may be expected in up to 50% of patients
- first 24 hours: death is caused by hemothorax, pneumothorax, pulmonary edema, shock, pleural effusion, and cardiac dysrhythmias
- later deaths: secondary to rupture, obstruction, or strangulation of GIT or diseases unrelated to hernia
- Recurrence rates 4% for dogs and 5% for cats.
What is the cause of a congenital pleuroperitoneal hernia?
Incomplete development or failure of fusion of the pleuroperitoneal membrane across the pleuroperitoneal canal
Results in absense of part of left lumbar crus (1-2cm defect) or absense of both crura and part of central tendon (large defect)
What is the cause of a congenital peritoneopericardial hernia?
Abnormal development of the transverse septum resulting in either a gap in the ventral diaphragm or an unusually thin ventral diaphragm which ruptures
result of dysembryogenesis, in which a connection remains between the pericardial and peritoneal cavity
PPH pathphys
- herniation of abdominal viscera into the pericardial sac.
- Peritoneopericardial diaphragmatic hernia is usually present at birth
- liver, falciform ligament, omentum, spleen, small intestine, and rarely the stomach.
- indirect pulmonary compression causes respiratory insufficiency.
- Incarceration, obstruction, or strangulation of abdominal viscera
- effusion in the pericardial sac or bloating of a herniated stomach produces cardiac tamponade; signs of right heart failure (reduced venous return)
- hepatic cysts, gallbladder torsion and rupture
What other abnormalities can be seen with PPDH? (6)
- Sternal defects
- Cranial ventral abdominal wall hernia
- Umbilical hernia
- Abnormal swirling of hair in sternal region
- Intracardiac defects
- Pulmonary vascular disease
diagnosis
- Weimaraners and long-haired cats of varying breeds
- incidental finding in 40% to 50% of affected cats,77 and 46.4% of dogs.
- Clinical signs may result from pathology in the gastrointestinal, cardiovascular, and respiratory systems
- muffled heart sounds
RADs
- cardiac silhouette is enlarged and usually rounded
- Discontinuity or overlapping of the diaphragm and the caudal cardiac border
- gas or feces-filled bowel within the cardiac shadow
- contrast stidies
- CT
ultrasound
- useful for confirming peritoneopericardial diaphragmatic hernia
- through the right fifth intercostal space or transabdominally
tx ppdh
- Cardiac tamponade from hepatic lobe effusion may require emergency pericardiocentesis
- Conservative treatment may be recommended for asymptomatic animals
- a midline celiotomy provides the best exposure
- pericardial sac is conjoined to the borders of the diaphragmatic defect and is continuous with the peritoneum
- closure can be accomplished in many without disruption of the pericardial-diaphragmatic junction (avoids pneumothorax and pleural effusion)
- in some cases the diaphragm may need to be incised to allow return of viscera to the abdomen.
- Once the pericardial sac is opened, so are the pleural cavities
small defects
- closed with an interrupted/ continuous suture pattern of monofilament absorbable material, commencing dorsally > ventrally.
- Air entrapped within sac may impede pulmonary expansion and should be drained by thoracocentesis
How can large PPDH defects be closed?
Transection of the pericardium cranial to its attachement to the diaphragm and used as a flap or free graft
phrenic nerves should be identified
What is the prognosis for PPHD?
Successful in 86%
Mortality rate 8.8%
complications
encountered in 78%
* hyperthermia (54%),
* tachypnea (14%),
* dyspnea,
* hypoventilation,
* hypoxia
* refractory pneumothorax.
What is diaphragmatic eventration?
Not a true hernia
Elevation of the dome of the diaphragm into the thoracic cavity. Can be congenital or acquired after phrenic nerve disease/injury
A ventral diaphragmatic advancement technique to repair a large congenital peritoneopericardial diaphragmatic hernia in a dog
Julie Hennet 2024
The ventro-central diaphragmatic defect was repaired with a pericardial flap, which subsequently failed 7 months later. The revision surgery was performed with a novel surgical technique. The defect was closed by means of incising the ventral attachments of the diaphragm either side of the defect and sliding it medially to allow a tension-free closure. The ventral aspect of the incised diaphragm was reattached with circumcostal sutures and the central defect closed. The dog recovered rapidly and without complication. An excellent outcome was reported after surgery.
Outcome after surgical and conservative treatments
of canine peritoneopericardial diaphragmatic hernia:
A multi-institutional study of 128 dogs
Morgan 2020
Retrospective study.
- surgically treated more likely younger, entire, have clinical signs and other congenital
abnormalities
- sx → 97% discharge; complications: intra- 22%, post- 41% - majority low grade
- major complications: pneumothorax, apnoea, SIRS, portal hypertension
- no hernia recurrence
- mortality: 5/91 sx, 4/37 conservative – attributable to PPDH
- MST: sx 8.2y, conservative 5y
A diagnosis of PPDH can confer a good long-term prognosis for both ST and CT dogs.
retrospective data set prevent us from making evidence-based conclusions about which dogs are likely to benefit from one approach vs the other
Robertson 2021 - In cats and dogs with traumatic diaphragmatic rupture, does surgical timing affect outcome?
veterinary evidence
review, no evidence to support effect of timing of surgery on mortality rates
- overall mortality rate across 10 studies 6.8-50%
- highest mortality rate in paper from 1980
- other papers report 6.8-26.7%
no statistically significant information available with only several retrospective studies published that are a low quality of evidence.
Pereira 2023 – acquired diaphragmatic hernia in 49 dogs, 48 cats
can vet j
time from trauma to development of signs no effect on survival
- complications: intra-op: 14/49 (28.6%) dogs, 5/48 (10.4%) cats
post-op: 7/49 (14.3%) dogs, 6/48 (12.5%) cats
- death: overall 14.4%; intra-op: overall 6.2%; post-op 8.2% (1h – 10d post)
- surgery <48hr after diagnosis → lower risk of death
Laparoscopic extra-abdominal transfascial suturing technique for diaphragmatic rupture repair in a cat
Filippo Cinti 2023
alternative to intracorporeal suturing → successful outcome with no complications
