Checando as 20 maiores tabelas do banco incluindo as tabelas LOB.

select * from
(SELECT segment_name,trunc(SUM(bytes) / 1024 / 1024,2) mb
FROM dba_segments
WHERE (
        OWNER = 'TESTE'
        )
    OR (
        OWNER
        ,segment_name
        ) IN (
        SELECT OWNER
            ,segment_name
        FROM dba_lobs
        WHERE OWNER = 'TESTE'
        )
group by segment_name
order by 2 DESC
)
where rownum <= 20;

Checando as tabelas vinculadas nos LOBs

col TABLESPACE_NAME format a20
col TABLE_NAME format a30
col OWNER format a10
SELECT *
FROM (
    SELECT c.OWNER
        ,c.segment_name
        ,c.segment_type
        ,c.TABLESPACE_NAME
        ,l.table_name
        ,trunc(sum(c.bytes) / 1024 / 1024 / 1024, 2) "SIZE GB"
    FROM dba_segments c
        ,dba_lobs l
    WHERE c.segment_name = l.segment_name
    GROUP BY c.OWNER
        ,c.segment_name
        ,c.segment_type
        ,c.TABLESPACE_NAME
        ,l.table_name
    ORDER BY 6 DESC
    )
WHERE rownum <= 10;