Table 1. The etiology and characteristics of the pleural effusion in the North-West of Iran .

Variables	CHF	Pneumonia	PTE	TB	Empyema	Infl.	SLE	Self-limited	Malignancy	Cirrhosis	ESRD	Nephrotic syndrome	Pancreatitis	Hypothyroidism
No. (%)		67 (30.0)	31 (13.9)	35 (15.7)	35 (15.7)	11 (4.9)	10 (4.5)	8 (3.6)	6 (2.7)	5 (2.2)	3 (1.3)	3 (1.3)	3 (1.3)	3 (1.3)	3 (1.3)
Age (y)		76.31	76.31	41.69	60.94	52.0	47.0	38.33	44.25	60.94	55.0	53.64	36.0	53.4	40.67
Gender (%)	M	58	63	26	50	100	100	33	50	51	87	45	33	80	33
	F	42	37	74	50	0	0%	67%	50%	49%	12%	54%	67%	20%	67%
Fluid nature (%)	Ts.	100	0	22	0	0	0	0	0	0	100	100	100	0	100
	Ex.	0	100	77	100	100	100	100	100	100	0	0	0	100	0
Disease course (%)	A	0	100	100	0	100	100	0	100	0	0	0	0	100	0
	SA	0	0	0	40	0	0	100	0	89	0	91	100	0	0
	C	100	0	0	60	0	0	0	0	6	100	9	0	0	100
Collection location (%)	R	38	45	49	40	67	0	0	0	42	100	27	33	0	0
	L	14	45	49	30	33	0	33	50	42	0	54	0	100	0
	B	47	0	2	30	0	100	67	50	14	0	18	67	0	100
Cell count (%)	PMN	71.92	78.38	76.71	29	80	37.5	26.66	40	76.14	53.75	65.45	65	66	71.66

CHF, congestive heart failure; PTE, pulmonary thromboembolism; TB, tuberculosis; Influ, influenza; SLE, systemic lupus erythematosus; ESRD, end-stage renal disease; NS, nephrotic syndrome; HypoT, hypothyroidism; SD, standard deviation; M, male; F, female; Ex, exudate; Ts, transudate; A, acute; SA, subacute; C, chronic; R, right; L, left; B, bilateral; PMN, polymorphonuclear.