Pyelonephritis

- A bacterial infection that affects the renal tubules, interstitium, and renal pelvis.
- One of the most common renal diseases. 
- Usually caused by gram-negative, rod-shaped bacteria that are part of the normal flora of the enteric tract. Most commonly caused by Escherichia coli, followed by Proteus, Klebsiella, and Enterobacter.
- The infecting bacteria are usually from the patient’s own enteric flora an example of an endogenous infection.
- Usually associated with a urinary tract infection (acute pyelonephritis) or involved with another precipitating condition, such as obstruction (chronic pyelonephritis).

Actinic keratosis
1. Dry, scaly plaques with an erythematous base.
2. Similar to actinic cheilosis, which occurs along the vermilion border of the lower lip.
3. Caused by sun damage to the skin.
4. Dysplastic lesion, may be premalignant.

 LUNG ABSCESS  Lung abscess is a localised area of necrosis of lung tissue with suppuration.

 It is of 2 types:

 - Primary lung abscess that develops in an otherwise normal lung. The commonest cause is aspiration of infected material.

 - Secondary lung abscess that develops as a complication of some other disease of the lung or from another site

ETIOPATHOGENESIS.

 The microorganisms commonly isolated from the lungs in lung abscess are streptococci, staphylococci and various gram-negative organisms. These are introduced into the lungs from one of the following mechanisms:

 1.   Aspiration of infected foreign material.

 2. Preceding bacterial infection.

 3.  Bronchial obstruction.

 4. Septic embolism.

 5. Miscellaneous (i) Infection in pulmonary infarcts, (ii) Amoebic abscesses, (iii) Trauma to the lungs. (iv) Direct extension from a suppurative focus.

Abscesses may be of variable size from a few millimeters to large cavities, 5 to 6 cm in diameter. The cavity often contains exudate. An acute lung abscess is initially surrounded by acute pneumonia and has poorly-defined ragged wall. With passage of time, the abscess becomes chronic and develops fibrous wall.

Microscopic Examination

The characteristic feature is the destruction of lung parenchyma with suppurative exudate in the lung cavity. The cavity is initially surrounded by acute inflammation in the wall but later there is replacement by exudate of lymphocytes, plasma cells and macrophages. In more chronic cases, there is considerable fibroblastic proliferation forming a fibrocollagenic wall.

Pernicious anaemia 

The special features are:

• Due to intrinsic factor deficiency
• Gastric atrophy with histamine fast achlorhydria
• Genetic basis (racial distribution and blood group A).
• Seen with auto immune disorders.
• Antibodies to parietal cells and to intrinsic factors are seen

Hypopituitarism

Hypopituitarism is caused by

1. Loss of the anterior pituitary parenchyma
    a. congenital 
    b. acquired  
    
2. Disorders of the hypothalamus e.g. tumors; these interfere with the delivery of pituitary hormone-releasing factors from the hypothalamus.  

Most cases of anterior pituitary hypofunction are caused by the following:
1. Nonfunctioning pituitary adenomas 
2. Ischemic necrosis of the anterior pituitary is an important cause of pituitary insufficiency. This requires destruction of 75% of the anterior pituitary. 

Causes include  

a. Sheehan syndrome, refers to postpartum necrosis of the anterior pituitary, and is the most cause. During pregnancy the anterior pituitary enlarges considerably because of an increase in the size and number of prolactin-secreting cells. However, this physiologic enlargement of the gland is not accompanied by an increase in blood supply. The enlarged gland is therefore vulnerable to ischemic injury, especially in women who develop significant hemorrhage and hypotension during the peripartum period. The posterior pituitary is usually not affected. 

b. Disseminated intravascular coagulation 
c. Sickle cell anemia 
d. Elevated intracranial pressure 
e. Traumatic injury
f. Shock states

3. Iatrogenic i.e.  surgical removal or radiation-induced destruction
4. Inflammatory lesions such as sarcoidosis or tuberculosis
5. Metastatic neoplasms involving the pituitary. 
6. Mutations affecting the pituitary transcription factor Pit-1 

Children can develop growth failure (pituitary dwarfism) as a result of growth hormone deficiency.

Gonadotropin or gonadotropin-releasing hormone (GnRH) deficiency leads to amenorrhea and infertility in women and decreased libido, impotence, and loss of pubic and axillary hair in men. TSH and ACTH deficiencies result in symptoms of hypothyroidism and hypoadrenalism. Prolactin deficiency results in failure of postpartum lactation. 

Fulminant hepatitis

Fulminant hepatitis leads to submassive and massive hepatic necrosis. 
a. Etiology. HAV, HBV, HCV, delta virus (HDV) superinfection, HEV, chloroform, carbon tetrachloride, isoniazid, halothane, and other drugs (acetaminophen overdose) all may cause fulminant hepatitis.
b. Clinical features include progressive hepatic dysfunction with a mortality of 25%-90%.
c. Pathology

(1) Grossly, one sees progressive shrinkage of the liver as the parenchyma is destroyed.