Congenital diseases of the kidneys part 2

 

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COMMON TYPES OF CONGENITAL ANOMALIES OF THE KIDNEYS AND URINARY TRACT :

  • Hydronephrosis

Vesikoureteral reflux, ureteropelvic junction obstruction, lower urinary tract obstruction

  • Renal parenchymal malformation

Agenesis, dysplasia, multicystic dysplastic

  • Disordered renal migration and collecting system formation 

Ectopic kidneys, horseshoe kidneys, duplicated collecting system

 

SYNDROMES THAT CAN BE ASSOCIATED WITH VACTERL :

  1. SINGLE GENE DEFECTS
  • Alagile syndrom (JAG1 gene)

Liver defects (bile duct paucity), heart defect (tetralogi of fallot, ventricle septal defect), facial defects (prominent forehead, short chin), renal defects (agenesis, hypoplasia, ureteropelvic junction obstruction, vesicoureteral reflux)

  • Holt-Oram syndrom (TBX gene)

Heart defects (atrial septal defect, ventricle septal defect), limb defects (polydactily, hypoplastic thumb), renal defects (ectopic kidneys, horseshoe kidneys, vesicoureteral reflux, hypoplasia)

  • Smith-Lemli-Opitz syndrome (DHCR7 gene inborn error in cholesterol synthesis)

Heart defects, limb defects, developmental delay, renal defects (ureteropelvic junction obstruction, hydronephrosis, dysplasia)

 

2. CHROMOSOMAL ANOMALIES (TRISOMY 18)

Heart defects, microcephaly, cleft palate, rocker bottom feet, growth delay, developmental delay, renal defects (horseshoe kidney, hydronephrosis, duplicated collecting system)

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Congenital diseases of the kidneys part 1

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Chronic kidney disease is a growing public health problem with a huge economic burden on society. In children, congenital anomalies of the kidneys and urinary tract are the most common cause for chronic kidney dieseases. Normal development of the kidneys and urinary tract progresses through a complex series of events and requires the expression of key transcription factors to occur with precision in the fetus.  It is now known that many genetic defects can lead to congenital anomalies of the kidneys and urinary tract. Most of them can be indentified prenatally with antenatal ultrasonography.  For infants born with severe renal impairment, transfer to a center specializing in infant dyalisis has been shown to be reasonably good, and survival improves further if kidney transplantation can eventually be achieved.

Congenital anomalies of the kidneys and urinary tract is not a single disease but merely descriptive for a large collection of diverse developmental disorders that arise during the formation of the kidneys, ureters, bladder and urethra in fetal life. They are not unified in the sense of having any single genetic etiology or common pattern of injury but can result from a wide array of genetic and/or environtmental factors that make an impact on the precise orchestration and timing of organogenesis of the kidneys and urinary tract.

Congenital anomalies of the kidneys and urinary tract include structural defects as antenatal hydronephrosis, renal agenesis, renal dysplasia, renal ectopia,ureteropelvic junction obstruction, vesicoureteral reflux, duplicated renal collecting systems, and posterior urethral valves.

Congenital anomalies of the kidneys and urinary tract can be seen with single gen mutations, such as Alagille syndrome, caused from a mutation in the JAG1 gene, and showing defects in the liver, heart, face and kidneys. The kidneys anomalies in the Alagille syndrome can vary in severity but can include renal agenesis, hypoplastic kidneys, , ureteropelvic junction obstructions and vesicoureteral reflux.

Other disorders with a congenital anomalies of the kidneys and urinary tract component will be associated with well recognized syndromes or nonrandom associations, displaying both renal and extrarenal defects, such as the VACTERL syndromes, which has the nonrandom pattern of vertebral abnormalities, anal atresia, cardiovascular defects, tracheoesophageal fistula, renal anomalies and limb defects. At least 3 of the defects need to be present for the present  for the condition to be classified  as VACTERL. The renal anomalies in VACTERL can vary in type and severity and may include hydronephrosis, ectopic kidneys, renal agenesis and dysplasia.  There are some well-described single-gene defects that can include features of VACTERL. Holt-Oram and Smith-Lemli-Opitz syndromes are 2 such conditions, with patients with Holt-Oram syndrome having defects in limbs and heart due to mutation in transcription factor TBX5 and patients with Smith-Lemli-Opitz syndrome exhibiting facial anomalies, limb defects and developmental delay due to mutation in the DHCR7 gene. VACTERL is also sometimes associated with chromosomal anomaly trisomy 18.

Most cases of VACTERL syndrome, however, are not associated with other syndromes outside of the VACTERL spectrum. The etiology of most cases of VACTERL syndrome is not clear, but several gene have been identified to be involved with this phenotype, including mutations in  mitochondial DNA, in the PTEN tumor-suppressor gene and in Fanconi anemia genes. This would to suggest that there are multiple potential genetic etiologies leading to a common constellation of defects and that VACTERL is not a single disease.

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Ventilator part 3

Ventilator machine

 

PULMONARY EFFECTS

Barotrauma may result in pulmonary interstitial emphysema, pneumomediastinum, pneumoperitoneum, pneumothorax, and/or tension pneumothorax. High peak inflation pressures (>40cm water) are associated with an increased incidence of barotrauma. However, note that separating barotrauma from volutrauma is difficult, since increasing barometric pressure is usually accompanied by increasing alveolar volume.

Experimental models of high peak inflation pressures in animals with high extrathoracic pressures have not demonstrated direct alveolar damage from increased pressure without increased volume as well. Thus, the statement that high airway pressures result in alveolar overdistention (volutrauma) and accompanying increased microvascular permeability and parenchimal injury may be more accurate. Alveolar cellular dysfunction occurs with high airway pressures. The resultant surfactant depletion leads to atelectasis, which requires further increases in airway pressure to maintain lung volumes.

High-inspired concentration of oxygen result in free-radical formation and secondary cellular damage. The same high concsntratiom of oxygen can lead to alveolar nitogen washout and secondary absorption atelectasis.

It has been theorized that pulmonary biophysical and biomecahanical injury in the presence of bacterial lung infections contributes to bacterial translocation and bacteremia.

 

CARDIOVASCULAR EFFECTS

The heart, great vessels, and pulmonary vasculature lie within the chest cavity and are subject to the increased  intrathoracic pressures associated with mechanical ventilation. The result is a decrease in cardiac output due to decreased venous return to the right heart (dominant), right ventricular dysfunction and altered left ventricular distensibility.

The decrease in cardiac output from reduction of right ventricular preload is more pronounced in the hypovolemic patient and in those with a low ejection fraction.

Exaggerated respiratory variation on the arterial pressure wave form is a clue that positive-pressure ventilation is significantly affecting venous return and cardiac output.  In the absence of an arterial line, a good pulse oxymetri wave form can be equally instructive. A reduction in the variation after volume loading confirm this effect. These effects will most frequently be seen in patients with preload-dependent cardiac function (that is, operating on the right side of the Starling curve) and in hypovolemic patients or in those with otherwise compromised venous return.

Increased alveolar-capillary permeability secondary to pulmonary inflammatory changes may, alternatively, contribute to increased cardiac output.

RENAL, HEPATIC AND GASTROINTESTINAL EFFECTS

Positive-pressure ventilation is responsible for an overall decline in renal function with decreased urine volume and sodium excretion.

Hepatic function is adversely affected by decreased cardiac output, increased hepatic vascular resistance and elevated bile duct pressure.

The gastric mucosa does not have autoregulatory capability. Thus, mucosal ischaemia and secondary bleeding may result from decreased cardiac output and increased gastric venous pressure.

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Ventilator part 2

Ventilator machine

 

METHODS OF VENTILATORY SUPPORT

  • Continous mandatory ventilation

Breaths are delivered at preset intervals, regardless of patient effort. This mode is used most often in the paralyzed or apneic patients because it can increase the work of breathing if respiratory effort is present. Continuous mandatory ventilation has given way to assist-control mode because assist-control with the apneic patient is tantamount to continuous mandatory ventilation. Many ventilators do not have a true continuous mandatory ventilation mode and offer assist-control instead.

  • Assist-control ventilation

The ventilator delivers preset breaths in coordination with the respiratory efforts of patient. With each inspiratory efforts, the ventilator delivers a full assisted tidal volume. Spontaneous breathing independent of the ventilator between assist-control  breaths is not allowed. As might be expected, this mode is better tolerated than continuous mandatory ventilation in patients with intact respiratory effort.

  • Intermittent mandatory ventilation

With intermittent mandatory ventilation, breath are delivered at a preset interval, and spontaneous breathing is allowed between ventilator-administered breaths. Spontaneous breathing occurs against the resistance of the airway tubing and ventilator valves, which may be formidable. This mode has given way to synchronous intermittent mandatory ventilation.

  • Synchronous intermittent mandatory ventilation

The ventilator delivers preset breaths in coordination with the respiratory effort of the patient. Spontaneous breathing is allowed between breaths. Synchronization between preset mandatory breaths and the patients’s spontaneous breath attempts to limit barotrauma that may occur with intermittent mandatory ventilation when a preset breath is delivered to a patient who is already maximally inhaled (breath stacking) or is forcefully exhaling.  One disadventage of synchronous intermittent  mandatory ventilation is increased work of breathing, though this may be mitigated by adding pressure support on top of spontaneous breath.

 

The initial choice of ventilation mode is institution and practitioner dependent.  Assist-contrl ventilation, as in continuous mandatory ventilation, is a full support mode in that the ventilator performs most, if not all, of the work of breathing. These modes are beneficial for patients who require a high minute ventilation. Full support reduces oxygen consumption and carbon dioxide production of the respiratory muscles. A potential drawback of assist-control ventilation in the patient with obstructive airway disease is worsening of air trapping and breath stacking.

When full respiratory support is necessary for the paralyzed patient following neuromuscular blockade, no difference exists in minute ventilation or airway pressures with any of the above modes of ventilation.

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Ventilator part 1

Ventilator machine

 

Intubation, with subsequent  mechanical ventilation, is a common life-saving intervention in emergency departement. Many different strategies of positive-pressure ventilation are available. These are based on various permutations of triggered volume-cycled and pressure-cycled ventilations and are delivered at a range of rates, volume and pressures. Poor ventilatory management can inflict serious pulmonary and extrapulmonary damage that may not be immediately apparent,

Because many of the effects of ventilator-induced lung injury are delayed and not seen while patients are in the emergency fepartement, much of our understanding of the adverse consequences of volume trauma, air-trapping, baro trauma and oxygen toxicity has come from the critical care literature. While the fundamental principles underlying mechanical ventilatory support have changed little over the decades, much progress has been made in our understanding of the secondary pathophysiologic changes associated with positive-pressure ventilation.

Ventilatory strategies have been devised for different disease processes to protect pulmonary parenchyma while maintaining adequate gas exchange, and they may be responsible for the increased rates of survival for pathologies such as acute respiratory distress syndrome.

MODES OF MECHANICAL VENTILATION

  • Volume-cycled mode

Inhalation proceeds until a set tidal volume is delivered and is followed by passive exhalation. A feature of this mode is that gas is delivered with constant inspiratory flow pattern, resulting in peak pressure applied to the airways higher than that required for lung distention (plateau pressure). Since the volume delivered is constant, applied airway pressures vary with changing pulmonary compliance (plateau pressure) and airway resistance (peak pressure)

Because the volume-cycled mode ensures a constant minute ventilation despite potentially abnormal lung compliance, it is a common choice as an initial ventilatory mode in the emergency departement. A major disadventage is that high airway pressures may be generated, potentially resulting in barotrauma. Close monitoring and use of pressure limits are helpful in avoiding this problem. Note that ventilators set to volume-cycled mode function well as monitors of patients pulmonary compliance, which will be decreased in physiological states such as worsening acute respiratory distress syndrome, pneumothorax, right mainstem intubation, chest wall rigidity, increased intra-abdominal pressure and psychomotor agitation. These pathophysiological states increase peak pressure and should be considered whenever pressure alarms are sounded.

  • Pressure-cycled mode 

A set peak inspiratory pressure is applied, and the pressure difference between the ventilator and the lungs results in inflation until the peak pressure is attained and passive exhalation follows. The delivered volume which each respiration is dependent on the pulmonary and thoracic compliance.

A theorical adventage of pressured-cycled modes is a decelerating inspiratory flow pattern, in which inspiratory flow tapers off as the lung inflates. This usually results in a more homogeneous gas distribution throughout the lungs. However, no definite evidence exists that this results in a reduction of the rate of ventilator-induced lung injury or overall mortality. Nevertheless, pressured-cycled ventilation has achieved considerable popularity in the intensive care setting for management of patients with acute respiratory distress syndomes, whose lungs are most likely to be characterized by a broad range of alveolar dysfuction and are also most vulnerable to the effects of barotrauma and volutrauma.

A major disadvantage is that dynamic changes in pulmonary mechanics may result in varying tidal volumes. This necessitates close monitoring of minute ventilation and limits the usefulness of this mode in many emergency departement patients. However, newer ventilators can provide volume-assured pressure-cycled ventilation, which incresae peak pressures as needed to deliver a preset minimum tidal volume.

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Congenital Lung Abnormalities

 

Structure Of Human Lung Anatomy Human Anatomy  Anatomy Of Lung Lobes Human Anatomy The Function

Structure Of Human Lung Anatomy Human Anatomy Anatomy Of Lung Lobes Human Anatomy The Function – HUMAN ANATOMY CHART

CONGENITAL PULMONARY AIRWAY MALFORMATION

Congenital pulmonary airway malformation are a heterogenous group of cystic and non cystic lung lesion that largely result from early airway maldevelopment. Congenital pulmonary airway malformation may communicate with the proximal airways. although this communicationis abnormal. Most of them derive their blood supply from the pulmonary artery and drain via pulmonary veins, with the exception of hybrid lesions, which can have a systemic blood supply.

A fast growing congenital pulmonary airway malformation may cause mediastinal shift and subsequent development of polyhydramnions and hydros. It well established  that indicators of a poor prognosis include large lesions, bilateral lung involvement and hydrops.

If not recognized antenatally, congenital pulmonary airway malformation are usually discovered between the neonatal period and 2 years of age, manifestating as respiratory difficulty or infection. Symptomatic infants who are diagnosed postnatally   are treated with surgical resection, which generally  consists of lobectomy or segmental resection.

 

CONGENITAL LOBAR OVERINFLATION

Congenital lobar overinflation also referred to as congenital lobar emphysema, is characterized by progressiive lobar overexpansion, usually with compression of the remaining (ipsilateral) lung. The underlying cause can be secondary to an intrinsic cartilaginous abnormality with resultant weak or absent bronchial cartilage,  extrinsic compression of an airway (eg, by a large pulmonary artery or a bronchogenic cyst). In either case, the collapsed airway can act as one-way valve, resulting in air trapping. Although the alveoli expand, the alveolar walls remain intact, therefore, the term emohysema is technically inaccurate.

Although most patients with congenital lobar overinflation present in the neonatal period, typically with respiratory distress, congenital lobar overinflation can be detected in utero by ultrasonography and magnetic resonance imaging.

 

BRONCHIAL ATRESIA

Bronchial atresia is a rare anomally resulting from focal obliterasion of a segmental, subsegmental or lobar bronchus. The bronchi distal to the stenosis are dilated and filled with mucus, with mild hyperinflation of the adjacent lung due to collateral air drift. In bronchial atresia, the airway is occluded rather than narrowed, consequently, there is no ball-valve effect as seen in congenital lobar overinflation.  Hence, the lobe or segment does not become nearly as hyperinflated as with congenital lobar overinflation. This may be the reason why congenital lobar overinflation manifest in the neonatal periods, whereas bronchial atresia is usually found incidently in adults.

 

BRONCHOGENIC CYSTS

Bronchogenic cysts are part of the spectrum of foregut duplication cysts and are  developmental lesion resulting from abnormal ventral budding of the tracheobronchial tree, probably  occuring between the 26th and 40th days of fetal life. They are mostly situated in the mediastinum, typically near the carina. Less commonly, they may occur within the lung parenchyma, pleura or diaphragm

Most bronchogenic cysts are found incidentally. In  infants, symptoms are generally caused by compression of the trachea or bronchii and esophagus, leading to wheezing, stridor, dyspnea and dysphagia. Intraparenchymal cysts may manifest with recurrent infection. Symptomatic cysts are generally resected surgycally.

 

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Pulmonary underdevelopment

Structure Of Human Lung Anatomy Human Anatomy  Anatomy Of Lung Lobes Human Anatomy The Function

 

Pulmonary underdevelopment has been classified into three categories:

  • Pulmonary agenesis

Complete absence of the lung parenchyma, bronchus and pulmonary vasculature

  • Pulmonary aplasia

Blind-ending rudimentary bronchus is present, without lung parenchyma or pulmonary vasculature

  • Pulmonary hypoplasia

Bronchus and rudimentary lung are present, however, the airways, alveoli and pulmonary vessels are decreased in size and number

 

It has been hypothesized that abnormal blood flow in the dorsal aortic arch during the 4th week of gestation (embryonic phase) causes pulmonary agenesis. Unilateral pulmonary agenesis is difficult to diagnose with prenatal ultrasonography;, however, it can be suspected on the basis of mediastinal shift. More than 50% of affected fetuses have other abnormalities involving the cardiovascular (patent ductus arteriosus, patent foramen ovale), gastrointestinal (tracheoesophageal fistula, imperforate anus), genitourinary, or skeletal (limb anomalies, vertebral segmentation anomalies) system.  Imaging findings in pulmonary aplasia and agenesis are similar, except for the presence of short blind ending bronchus in aplasia. Postnatal radiography demonstrates diffuse opacification of the involved hemythorax with ipsilateral mediastinal shift and computed tomography helps confirm the absence of the lung parenchyma, bronchus and pulmonary artery on the involved side.

Pulmonary hypoplasia can be primary or secondary. Primary pulmonary hypoplasia, in wich a cause cannot be elucidated , is much less common than secondary hypoplasia.   The majority of cases of pulmonary hypoplasia are secondary to a process limiting the thoracic space for lung development, which can be either intrathoracis or extrathoracic. The most common intrathoracic cause is congenital diaphragmatic hernia, which is left sided in 75-90% of cases, right sided in 10%, and bilateral in 5%. Left-sided congenital diaphragmatic hernia is relatively easier to detect due to the presence of an identifiable fluid-filled stomach in the thorax. In right-sided congenital diaphragmatic hernia, the liver herniates into the chest, which may be difficult to detect due to the solid echotexture of the liver. The herniated liver can be confused with a mass originating in the lung. Color Doppler imaging maybe helpful in identifying the portal and hepatic veins. Magnetic resonance imaging provides greater soft tissue contrast, which is useful in assessing the size of the hernia and the location of other abdominal viscera. Other intrathoracic causes of the pulmonary hypoplasia include congenital pulmonary airway malformations, broncho-pulmonary sequestrations,  a cardiac or mediastinal mass, lymphatic malformations, and agenesis of the diaphragm.

The most common extrathoracic cause of pulmonary hypoplasia is severe oligohydramnions, occuring secondary to either fetal genitourinary anomalies such as renal agenesis, cystic renal dysplasia and urinary tract obstruction or prolonged rupture of membranes. A hypoplastic thorax, occurs in skeletal dysplasias, such as thanatophoric dysplasia or Jeune syndrome, in wich a small and rigid thoracic cage causes pulmonary hypoplasia. Antenatally, thoracic circumference measurements are obtained in an axial plane at the level of the four-chamber view of the heart.

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